Police say they are investigating the possibility of a “terrorism hoax” after a pair of anonymous phone calls prompted a Toronto-to-Pakistan flight to make an emergency landing in Sweden on Saturday.

A Canadian traveller was taken into custody because of the phone calls — made to Toronto-area police — which warned that a man onboard Pakistan International Airlines Flight 782 was carrying explosives.

None were found, and the traveller, a man of Pakistani descent believed to be about 30 years old, was eventually released, though not until after the plane had left without him.

RCMP Sgt. Marc Laporte said one call was made to police around 3 p.m. ET, and the other after the 5 p.m. flight had departed.

By the time the message was relayed, the Boeing 777 — with 255 passengers, including 102 Canadians, and 18 crew members — had already left Toronto.

The pilot received the warning in the air, and proceeded to ask Swedish police late Friday if he could set down in Stockholm.

“Because of the nature of the information and the potential threat — obviously we couldn’t confirm the reliability of the information in time — we needed to take action right away,” said Laporte.

He stressed the investigation is still in its early stages, and that police have not yet determined if the phone calls were a hoax.

However, Laporte said, if it was a hoax the caller could face one of two criminal charges: public mischief, described as “leading police into a false investigation,” or a “terrorism hoax.”

“There is a specific offence for (the latter charge) because the nature of the reaction from the authorities would be different,” Laporte told Postmedia News.

“Sometimes with these investigations, if it’s deemed to be a hoax, it actually takes longer because we have to more or less eliminate all of the other options.”

The plane was diverted to Arlanda airport, the main airport for the Swedish capital, said Stockholm district police spokesman Janne Hedlund.

“A woman called police from a pay phone in Canada and told Canadian police about the man. She said the man may have had explosives, but he passed security checks,” Hedlund said.

The plane was on the tarmac in Stockholm for more than nine hours while authorities investigated the threat, checking all of the luggage as well as the aircraft.

Ulf Lindgren of the Stockholm district police said the man left behind by his flight would soon leave Sweden.

“The prosecutor . . . couldn’t find any need to keep him locked up,” he said. “He’s now free to go and free to leave the country.

“Swedish police is going to take care of the practical things, so he can continue his journey to Pakistan as soon as possible.”

Airline spokesman Sultan Hasan said all passengers — with the exception of the detained Canadian — re-boarded and headed for Manchester, England. He said that after a stop there to change crew, the flight would continue on to Karachi in Pakistan.

“We were very concerned and it’s good news they were all safe,” Hasan said. “The plane would not have taken off unless it was cleared by the security team.”

with files from Amy Husser, Postmedia News