A middle-aged man died Wednesday minutes after he was summoned to a police station in Kolkata in connection with a mobile phone theft. The death of Ashok Kumar Singh during interrogation at Amherst Street police station has sparked controversy with the family alleging that he was physically tortured by the officials, sources said.

The family members are likely to approach Calcutta High Court on Thursday, they said.

An additional police officer of Kolkata Police rank is investigating the case in which Singh was allegedly beaten to death by the policemen.

Senior officers at the police headquarters have prepared a list of the names of the police personnel who were present at the time of the incident, including the officer-in-charge and additional officer-in-charge of Amherst Street police station.

The relatives of Ashok Kumar Singh, a resident of Beniatola Lane who ran a small business, have claimed that he was tortured and beaten up in the police station following which he collapsed and died.

According to the police, the mobile phone used by Singh was a stolen one which he had allegedly told the police of buying at Rs 200 from someone. The monitoring cell of Kolkata Police North Division contacted him around 5 pm and asked him to be present at the Amherst Street police station along with the phone, officials said.

The residents of the area blocked the College Street Square at night. As per sources, the police are awaiting the detailed post-mortem report.

Meanwhile, the BJP has demanded a CBI probe into the incident.