The plane landed in Stockholm after a tip that a passenger was carrying explosives[Reuters]

Canadian police have said they are looking into whether a bomb alert which prompted the emergency landing of a Pakistani plane in Sweden was a hoax.

A man who had been arrested on suspicion of carrying explosives was released without charge after being questioned by Swedish police on Saturday.

"The suspicions against the man were not sufficiently strong for an arrest order and he is therefore free to leave Sweden," the prosecutor's office said in a statement.

No explosives were found on the man or on board the plane, which was travelling from Toronto to Karachi. 

The pilot had been asked to land in Stockholm, the Swedish capital, after a woman in Canada called the police from a payphone to say a man on the plane had explosives.

Under Canadian law, a "terrorist hoax" is a crime punishable with prison time, Marc Laporte, a spokesman with the Royal Mounted Police in Toronto, told the AFP news agency.

The passengers on board were not told the real reason for the emergency landing until they were already on the ground.

Crew members instead told them the plane was landing for "technical reasons".

Before the man was released, the plane departed for Manchester in England for a change of crew, before resuming its flight to Pakistan.

Ulf Lindgren, a Stockholm district police spokesman, said the man, whose identity was not released, received help with the practical details of how to reach his planned destination.

Police officials had earlier said the man was not on any international no-fly lists and had cleared a security check in Canada.

He did not resist when police took him into custody and the evacuation of the 273 passengers on board the plane was said to have been calm.