A gang broke into a jewellery shop in Madhyamgram late on Thursday and left with gold and silver ornaments worth around Rs 24 lakh.
The burglars entered the shop by making a hole in an adjoining wall. From its size, police surmise they must have used a child to enter the shop.
Owner Suman Dhar detected the theft at 9am on Friday when he came to open the shop.
Preliminary investigation suggests the bore was so small that only a child less than 10 years old that too, one who is quite thin could have entered through it, said an officer.
Last month, a gang of robbers had raided a house in Naihati, and the victims had told cops there had been a child in the gang.
We are trying to ascertain whether the Madhyamgram theft was the handiwork of the same gang, the officer said.