The police team searching for Calcutta High Court's former judge CS Karnan knew about his hiding place in Coimbatore in Tamil Nadu for three days before moving in to arrest him, the West Bengal police chief said on Wednesday.

"We knew about his (Karnan's) whereabouts three days back. We were tracking phone calls of people close to him and we also have our own sources," Director General of Police Raj Kanojia said.

Kanojia spoke at the Chennai airport before boarding a flight to Kolkatta.

According to him, this was a unique case he had handled in his entire service and "maybe no other police officer will be handling such a case in a long time to come".

"Tracking Karnan was difficult. It was a difficult case," Kanojia said.

Karnan, who was sentenced to six months imprisonment by the Supreme Court for contempt but was untraceable, was arrested near Coimbatore on Tuesday. Coimbatore is around 500 km from here.

Karnan was eluding arrest for more than a month.