Rural Superintendent of Police A Gopinathan, who is in charge of the case, told UNI that a police team raided the shop of the scrap dealer, Mustaffa, and recovered the casings meant for making rocket parts and worth Rs two lakhs.

A wholesale scrap dealer in Tirunelveli of Tamil Nadu, who received the casings from Mustaffa returned them to him through rail after learning about the theft.

Though the police had stepped up security at the city railway station, Mustaffa managed to collect the parcel. Police teams had also been despatched to Madurai and Tirunelveli in connection with the case.

Gopinathan said the three youths, who trespassed into the high-security of ISRO and walked away with the alloy casings imported from France,were arrested. The role of some Central Industrial Security Force (CISF) jawans in the theft was also being probed, he added.

According to sources, as many as 20 alloy casings were brought to the centre on December 23 from Tamil Nadu.