The main accused in the sensational theft of rare Brazilian monkeys from a zoo here escaped from police custody on Monday while he was being brought in a train from Chhattisgarh, where he was arrested on Saturday.

Rajesh Saikia alias Raj, who was being brought to Kolkata on the Ahmedabad Express on transit remand, was found “missing” when the train stopped at Jharsuguda station in Orissa, a top police official said.

According Kolkata police sources, two police officers along with two officials of Alipore zoo, from where the marmosets were stolen last month, were escorting Saikia.

“Immediately an FIR was lodged and a massive manhunt started,” said the official.

However, no one has been arrested so far.

Chhattisgarh police had arrested Saikia last week from Durg district and rescued seven of the eight monkeys stolen from the zoo. One of the monkeys had died.

Police had said they were investigating whether he had links with any international gang involved in smuggling of rare animals.

Acting on information provided by him, Sujoy Das alias Bubai Bangali was arrested from Dum Dum in North 24-Parganas district.

Meanwhile, the monkeys reached the zoo safely this afternoon. They were ferried on the same train.