Kolkata, Feb 7 (IANS): Bhopal resident Udayan Das, who allegedly killed his parents and live-in partner, was sent to eight days police custody in West Bengal on Tuesday, police said.

"A lot of interrogation needs to be done. We need to find out his real motive for murdering his live-in partner Akansha Sharma," Bankura Superintendent of Police Sukhendu Hira told IANS over phone.

"During initial interrogation, Das said he killed his partner in a fit of rage," he said.

Das was brought to Bankura from Kolkata airport on Monday night under police escort.

Das' lawyer pleaded that his client should not be handed over to the police immediately on grounds of "insanity".

"My client is a psychiatric patient. He needs to go through mental treatment first. We cannot depend on his statements as he is not mentally stable," the lawyer said at the Bankura District Court premises.

His arrival was delayed as IndiGo Airlines refused to ferry Das on board its Raipur-Kolkata flight as the police escort did not possess valid security documents.

Das was arrested on February 2 by the West Bengal Police on charges of murdering Sharma and entombing her body in a concrete block inside his house in Saketnagar in Bhopal. 

Police said he admitted to killing his own parents in 2010 and burying them in the garden of their family home in Raipur.

Two skeletons, believed to be of his parents, were dug out from the Chhattisgarh residence on February 5.