The project, expected to be completed in 2015 at an estimated cost of $250 million, has been cleared by the Ministry of Environment (India) for construction in the Bodi West Hills Reserved Forest in the Theni district of Tamil Nadu. When completed, the INO will house the world's most massive magnet, four times larger than the 12,500-tonne magnet in the Compact Muon Solenoid detector at CERN in Geneva, Switzerland. 
The possibility of a neutrino observatory located in India was discussed as early as 1989 during several meetings held that year. Since then this question comes up, off and on, in many discussions. The issue was raised again in the first meeting of the Neutrino physics and Cosmology working group during the Workshop on High Energy Physics Phenomenology (WHEPP-6) held at Chennai in January 2000 and it was decided then to collate concrete ideas for a neutrino detector.
Further discussions took place in August 2000 during a meeting on Neutrino Physics at the Saha Institute of Nuclear Physics, Kolkata, when a small group of neutrino physics enthusiasts started discussing the possibilities. The Neutrino 2001 meeting was held in the Institute of Mathematical Sciences, Chennai during February 2001 with the explicit objective of bringing the experimentalists and theorists in this field together. The INO collaboration was formed during this meeting. The first formal meeting of the collaboration was held in the Tata Institute of Fundamental Research, Mumbai, during September 6 and 7th, 2001 at which various subgroups were formed for studying the detector options and electronics, physics goals and simulations, and site survey.
In 2002, a document was presented to the Department of Atomic Energy, (DAE) which laid out an ambitious goal of establishing an India-based Neutrino Observatory, outlining the physics goals, possible choices for the detector and their physics. Since then many new and fast paced developments have taken place in neutrino physics. The award of the Nobel Prize in Physics (2002) to the pioneers in neutrino physics is a measure of the importance of this field.
As a result of the support received from various research institutes, universities, the scientific community and the funding agency, the Department of Atomic Energy, a Neutrino Collaboration Group (NCG) was established to study the possibility of building an India-based Neutrino Observatory (INO). The collaboration was assigned the task of doing the feasibility studies for which funds were made available by the DAE. A memorandum of understanding (MoU) was signed by the directors of the participating institutes on August 30, 2002 to enable a smooth functioning of the NCG during the feasibility period. The NCG has the goal of creating an underground neutrino laboratory with the long term goal of conducting decisive experiments in neutrino physics as also other experiments which require such a unique underground facility.
On November 20, 2009, Ministry of Environment (India) Minister Jairam Ramesh in a letter to Anil Kakodkar, Secretary, Department of Atomic Energy and Chairman, Atomic Energy Commission of India, denied permission for the Department of Atomic Energy to set up the India-based Neutrino Observatory (INO) project at Singara in Nilgiris, as it falls in the buffer zone of the Mudumalai Tiger Reserve (MTR). Jairam Ramesh said that based on the report of Rajesh Gopal, Additional Principal Chief Conservator of Forests (PCCF) and Member-Secretary of the National Tiger Conservation Authority (MS-NTCA), the Ministry cannot approve the Singara site. The report says:
"The proposed project site falls in the buffer zone of Mudumalai Tiger Reserve and is in close proximity to the core/critical tiger habitats of Bandipur and Mudumalai Tiger reserves. It is also an elephant corridor, facilitating elephant movement from the Western Ghats to the Eastern Ghats and vice-versa. The area is already disturbed on account of severe biotic pressure due to human settlements and resorts and that the construction phase of the project would involve transport of building materials through the highways passing through the core area of the Bandipur and Mudmulai Tiger Reserves.
Instead, he suggested an alternate site near Suruli Falls, Theni District in Tamil Nadu. The Minister said this site did not pose the same problems that Singara posed and environmental and forest clearances should not be a serious issue. He also assured the DAE that the Ministry would facilitate necessary approvals for the alternative location. Dr. Naba K. Mondal of the Tata Institute of Fundamental Research, who is the spokesperson for the INO project said:
"But Suruliyar too is in a reserved forest area that is dense and would require cutting down of trees, something that was not required at Singara. Can the government assure us that forest clearance for this site will be given," he asks. "Alternatively, we can move to the nearby Thevaram, which is about 20-30 km away from the Suruliyar falls. This forest area has only shrubs but there is no source of water here and water will have to be piped over a distance of 30 km,"
On 18 October 2010, the Ministry of Environment & Forests approved both environment and forest clearance for setting up the observatory in the Bodi West Hills Reserved Forest in the Theni district of Tamil Nadu. The project is expected to be completed in 2015 at an estimated cost of $250 million. 
Memorandum of Understanding (MoU) spelling out the operational aspects of the project and the mode of utilisation of available funds was signed by seven primary project partners: Tata Institute of Fundamental Research (TIFR), Mumbai, Bhabha Atomic Research Centre (BARC), Mumbai, Institute of Mathematical Sciences (IMSc), Chennai, Saha Institute of Nuclear Physics (SINP), Kolkata, Variable Energy Cyclotron Centre (VECC), Kolkata, Harish Chandra Research Institute (HRI), Allahabad and Institute of Physics (IOP), Bhubaneswar.
Thirteen other project participants include: Aligarh University, Aligarh, Banaras University, Varanasi, Calcutta University (CU), Kolkata, Delhi University (DU), Delhi, University of Hawaii (UHW), Hawaii, Himachal Pradesh University (HPU), Shimla, Indian Institute of Technology, Bombay (IITB), Mumbai, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, North Bengal University (NBU), Siliguri, Panjab University (PU), Chandigarh, Physical Research Laboratory(PRL), Ahmedabad, Sálim Ali Centre for Ornithology and Natural History (SACON), Tamil Nadu and Sikkim Manipal Institute of Technology, Sikkim.
The primary research instrument will consist of a 50,000 ton magnetized iron particle physics calorimeter with glass Resistive Plate Chamber (RPC) technology as the sensor elements.
The INO design is mostly based on the monolith experiment that could not go beyond the proposal Stage. The detector was expected to start collecting data in the year 2012. The location of INO has attracted a lot of attention from the neutrino physics community as the distance between INO and CERN is very close to "Magic Baseline" - a distance at which the effect of the CP phase on the measurement of θ13 is minimal. The project has been hit by lack of skilled man power and opposition by environmentalists. In 2008, INO started a graduate training program leading to Ph.D. Degree in High Energy Physics and Astronomy to deal with the shortage of particle physicists. 
The Primary goals of the INO are the following 
Unambiguous and more precise determination of Neutrino oscillation parameters using atmospheric neutrinos.
The INO detector consists of 6 centimeters (2.4 in) thick Iron plates as passive material, with RPCs in between as active material.
A prototype of the INO detector with 14 layers, measuring 1m x 1m x 1m is already operational in the VECC, Kolkata. The 35 ton prototype is set up over ground to track cosmic muons. 
The location of the site was supposed to be Singara 11°32′N 76°36′E 5.5 kilometers (3 mi) southwest of Masinagudi in the Nilgiri Hills of South India. The site has been changed due to protests from environmental groups. The INO will now be built at Bodi West Hills in Theni district, southern India. 
^ a b c d Mondal, Naba K. (January 2004). "STATUS OF INDIA-BASED NEUTRINO OBSERVATORY (INO)". Proceedings Indian National Science Academy 70, A: 71–77. Retrieved 4-3-2008.