Image caption The thick layer of rock in the West Bodi hills will provide a natural filter

India's Department of Atomic Energy has been given clearance to build a multi-million dollar underground facility to study particles called neutrinos.

The environment and forests ministry gave the go-ahead for the observatory to be built in the Bodi West hills on the coast of southern Tamil Nadu state.

The facility costing $270m will be only the fifth of its kind in the world.

Correspondents say it is one of the biggest and most ambitious scientific projects ever undertaken by India.

One of the scientists leading the project says it could help India gain a leading role in the field of particle research.

Neutrinos are elusive, nearly mass-less elementary particles, sometimes called "ghost particles".

'Natural rock cover'

About 90 scientists from 26 organisations will be involved in the Indian Neutrino Observatory (INO), organisers say.

Construction work is expected to begin soon.

The facility will be built in Theni district under the Western Ghats mountains, about 110km (70 miles) south of the temple town of Madurai.

A cavern to house the lab and a 2km-long tunnel will be built under the hills over the next few years. Scientists will use a 50-kiloton electromagnet to carry out experiments.

"Neutrinos are tiny, neutral, elementary particles found abundantly in the cosmos. The Sun and all other stars produce neutrinos abundantly through nuclear fusion and decay processes. Neutrinos rarely interact and pass unhindered through all objects including the Sun and the Earth," says Dr Chinnaraj Joseph Jaikumar, chairman of the INO cell in Madurai.

"We have chosen a place where natural rock cover of over 1,000m thickness is available. The hard rocks will act as a natural filter allowing only the neutrino particles to reach the laboratory."

Dr Jaikumar expects the project to enhance understanding of the universe and the Earth's structure, as well as volcanic activity and how tsunamis are formed.

A site near the southern hill station of Ooty was originally chosen for the project, but did not get clearance after local protests.

Activists near Theni fear locals may suffer restricted access to the area owing to the sensitivity of the project.