Hundreds of policemen and Atomic Energy Commission squads have fanned out in the northeast Indian state of Assam to find a missing radioactive gamma-ray camera.
A red alert was declared after the iridium camera - with a radioactive pellet used for examining oil pipeline weldings - was stolen while being transported from Lakhimpur to Digboi by bus last week.
P. C. Saloi, the regional police chief supervising the massive search operation, suspects the involvement of several criminals.
Assam government and Atomic Energy Commission officials said that the theft was reported to the police by the Calcutta-based firm that owns the camera, Radiography Inspection Services. The company had been transporting it to the state-owned Indian Oil Refinery at Digboi but on reaching its destination, the firm discovered the camera was missing from the baggage compartment of the public bus.
Commission secretary K. S. Parthasarathy said transporting sensitive equipment by bus was against safety norms and strictly prohibited.
He said radioactive equipment is usually carried in specially designated vehicles.
Jyotisana Chatterje, a scientist at Calcutta's Saha Institute of Nuclear Physics, said the missing camera's radioactive component could cause cancer.
Last month International Atomic Energy Agency (IAEA) director-general Mohamed El-Baradei warned that India was among 100 countries which lacked the control mechanisms to prevent the theft of radioactive materials.
But the charge was denied by commission chairman Anil Kakodkar, who said the radioactive protection infrastructure in place in India was among the best in the world.
Mr Kakodkar admitted there was a grave risk of radiation if the stolen camera was tampered with.
According to the IAEA, the world's worst case of radioactive contamination took place after scavengers dismantled a metal canister from a radiotherapy machine at an abandoned cancer clinic in the Brazilian city of Goiania in 1987. The radioactive substance released killed four people and contaminated over 200 in Goiania.