A police team has left for Bihar in search of the men who had robbed a New Alipore house after gagging a resident in her 80s on Wednesday afternoon.

"At least one of the three men who had raided 195/1 SN Roy Road, near the New Alipore fuel pump, lives in Bihar. We suspect the gang has fled to that state. A police team has left for Bihar," an officer involved in the probe said.

Several persons were detained on Thursday for questioning.

The three men who claimed to have been looking for the job of domestic help gagged Shila Khemka, in her 80s, and robbed Rs 2 lakh and jewellery worth Rs 3 lakh.

Sources said Khemka was alone in the house when the gang knocked on the door in the afternoon. When the woman opened the door, one of them introduced himself as Ramesh Prajapati and said Shankar had sent them.

"Shankar had worked in the house years ago. Since quitting the job, he has been supplying domestic help to the Khemkas whenever they needed one," a police officer.

The woman let in the trio, only to be overpowered and gagged by them.

The heist came to light hours later when Khemka's daughter-in-law Shruti returned home and found her tied up in the corner of a room. All the cupboards were ransacked.

The robbery highlights how vulnerable Calcuttans are to crimes committed by domestic help.