Thiruvananthapuram: The shocking case of a college professor being hacked and his right hand being chopped off in Muvattupuzha in Kerala state turned murkier yesterday, with one of the police officers investigating the crime receiving a death threat.

Circle inspector, Famous Varghese, who is part of the police team that is investigating Sunday's attack on professor T.J. Joseph of the Newman College, in Thodupuzha, central Kerala, received a death threat, apparently from one of the suspects involved in the incident.

The professor had been under suspension after he incorporated a controversial question in the Malayalam examination in his college which was considered derogatory to Muslims.

Joseph had been arrested in connection with the case but had secured bail. His car was apparently waylaid by a gang in a van on his way back home from church on Sunday and attacked in front of his sister, a nun who is based in New Zealand, and his octogenarian mother.

A team of specialist doctors at a hospital in Ernakulam performed a 15-hour operation on Joseph to reattach his severed hand.

Police have arrested two suspects in the case. The police team has also seized the van in which the suspects are believed to have gone to commit the crime.

It is suspected that an activist of an organisation named Popular Front is behind the telephonic threat to the police officer.

Following the attack on the professor, his family revealed that the attackers had visited his house many times in the past couple of months, in different guises, sometimes pretending as book salesmen and at other times as insurance agents. The family had filed a police complaint, but it was only a week later that police had followed up on the matter, they said.