Officials at Canada's largest airport have apologized after a "security incident" forced an Air Canada plane headed for Brazil to return to Toronto, hours into a flight to Sao Paulo.

Air Canada Flight 090 departed Pearson International Airport at 12 a.m. ET, but was forced to turn back due to a security breach at the airport that happened just before 11 p.m. In that incident, a man had reportedly passed through security without being properly screened.

This photo, sent to CBC News by a passenger on the flight, shows passengers in a waiting room after their flight to Brazil was turned back early Thursday. (Submitted by Olivier Cullen)

All departures were held on the ground while security and police searched for the man.

Air Canada told CBC News Thursday that Transport Canada ordered that the plane return to Pearson about four hours into the flight. A website flight tracker showed the plane making a 180-degree turn just north of Turks and Caicos Islands.

The Greater Toronto Airport Authority's statement issued Thursday says it "takes all issues related to airport security very seriously," and will complete an "internal assessment" about the incident.

"In the interim, enhanced security measures have been put in place. Given the incident involves airport security, we cannot share specific details. We sincerely apologize to the passengers who were inconvenienced."

When the plane landed in Toronto at about 6:30 a.m., it was greeted by a large group of police and airport security. The plane was searched, passengers were led off the plane and questioned and one man was taken into custody.

It was the longest flight from Toronto to Toronto that I've ever been on. - Olivier Cullen, passenger

Peel Regional Police issued a tweet just after 11 a.m. saying there was "was no criminality involved" and that the investigation is "completed."

Const. George Tudos, a spokesperson for the police force, told CBC News that the search at Pearson had affected other flights.

"We were assisting airport authorities to try to locate a male party and the call was for a potential security breach at the airport," Tudos said in an interview.

"So this may have halted a few flights from departing at their regular times, just to facilitate our search to locate this party."

A heavy security and police presence greeted the plane when it returned to Pearson Airport. (Submitted by Chantal Vallee) Passengers from the Air Canada plane that was bound for Sao Paulo were booked on another flight, which left mid morning, but many were left wondering why their plane was forced to return to Canada, making them endure an hours-long delay.

"It was the longest flight from Toronto to Toronto that I've ever been on," passenger Olivier Cullen told CBC News. Cullen, like many of the passengers, were headed to Brazil for the FIFA World Cup. He said many on the flight had tickets for this afternoon's game between England and Uruguay — a match they will now miss.

"There was a lot of confusion in the air," said Cullen. "People are upset, but some people are taking it in stride."

After departing again for Brazil, passenger and Canadian basketball coach, Chantal Vallee said in a tweet: "Yeah!! Boarding now back to Sao Paulo! I think that will mean 18 hours of flying in 24 hours."