Explosive material was found on a passenger plane after it landed in Thiruvanantapuram in southern India, but it was not immediately clear whether it was meant to be detonated on a flight, police said on Sunday.

Forensic experts were inspecting a package the size of a cricket ball found in a bag inside the cargo hold of an aircraft after all passengers had disembarked, Ajith Kumar, the city's police commissioner, told Reuters by phone.   

Kumar suggested the explosives might have been placed in the hold after the plane landed.

"The police will investigate whether the explosive material was placed in the aircraft at Thiruvananthapuram airport," he said.

The plane was moved to an isolated area in Thiruvananthapuram airport in the state of Kerala.

India remains jittery about the threat of militant attacks. A blast in the western city of Pune killed 16 people in February, the first major militant strike since the 2008 Mumbai attacks. - Reuters