The 70-year-old mother of a sub-inspector of police and resident of a village on Raiganj outskirts was found dead with deep wounds on her head on Monday late night.

Raiganj police suspect she was murdered and have detained one of her grandsons for interrogation.

Sources said victim Batashi Burman, a resident of Joynagar village of Raiganj block, has three sons one of whom is Mohini Burman, who works in the state police force and is posted in Bagdogra police station of Darjeeling district. Batashi used to reside with her two other sons and their families.

Police said that Shankar Burman, one of Batashi’s grandsons and Mohini’s nephew, had woken up on Monday night to attend nature’s call when he noticed that the door of his grandmother’s room was ajar.

“He said that as he peeped in, he found blood oozing from the old lady’s head, and raised an alert. Soon, we got information and a team was sent to the spot,” said a police officer.

As news spread, neighbours swarmed into the victim’s house. Sub-inspector Mohini was told about the fatal attack on his mother. He reached Raiganj from Bagdogra early on Tuesday.

Police recovered the body and initiated a probe. “We suspect she has been bludgeoned to death. Some blunt weapon was used and she was hit on the right side of her head. The post-mortem reports will confirm the cause of her death,” an officer said.

Neighbours are perplexed over the incident. Batashi had cordial relations with them and they had never heard any dispute within the family, neighbours have said.

Police detained Shankar who they suspect might be involved in the crime.

“We are not ready to buy what he has told us. We have also learnt that he is a habitual drunkard and we need to interrogate him. Our officers are trying to find out the motive behind the murder,” said Sumit Kumar, the SP of North Dinajpur.