The city police on Friday started a suo motu case of culpable homicide not amounting to murder against “unknown person” in connection with the death of civil engineer Rishav Mondal.

Mondal, 25, had died of electrocution allegedly after coming in contact with a lamp post on a waterlogged footpath near Raj Bhavan on Tuesday evening after a spell of heavy rain.

“Today, a case has been started under Section 304 of the Indian Penal Code for Rishav Mondal’s death. A detailed inquiry has been launched to fix responsibility for the death,” said a senior police officer of the central division.

Sources in Lalbazar said the police have conducted the forensic examination of the lamp post and the bunch of wires that were found to be wrapped around it.

“It needs to be ascertained which of these wires caused the electrocution. Then we will try to establish the source of power of that particular wire,” said an officer in Lalbazar.

Several eyewitnesses and shopkeepers in the area have been examined.

Prima facie, many have been found to be illegally drawing electricity from the main lines.

Outgoing Mayor Firhad Hakim on Wednesday had put the blame of the incident on “electricity theft” and “hooking” that he said, could have caused the electrocution.

Investigators said it was too early to confirm the individual or agency which was behind the power supply.

A senior officer said, “One thing is clear. Whoever is responsible for this (electricity theft) had full knowledge about the consequences of the act. Hence, a case under section 304 has been initiated.”

The charge, if proved, could lead to a maximum punishment of 10 years of imprisonment.

Mondal’s family, who are from Murshidabad, had not lodged a formal police complaint till Friday evening.