Montreal police have cordoned off a five-block residential section of a LaSalle neighbourhood tonight after security officials at Pierre Elliott Trudeau Airport found a suspicious package that caused panic and delays.

Several homes were evacuated and about 20 residents were displaced as officers taped off a security perimeter.

Police said they were going to search a nearby house.

Montreal police spokesperson Ian Lafrenière dismissed reports that a suspect who was detained had been carrying multiple passports. He said police have already searched the suspect's vehicle, but have not yet questioned him.

"We're just there to confront him with some facts," Lafrenière said.

He added: "We have a puzzle here, and we're missing some pieces."

The suspicious suitcase was found near the U.S. customs area around 5:45 a.m., authorities said.

It was later removed and analyzed and a man in his 70s, who is known to police, is now in custody, CBC's Alison Northcott reported from the scene.

Northcott said authorities are trying to determine the contents of the suspicious luggage. She said authorities did not find explosives.

"[Authorities] say there were other materials in that suitcase that made them very concerned, but they wouldn't elaborate on what that was," Northcott reported.

The detention of the suspect led investigators to the neighbourhood in LaSalle, just west of Montreal.

Following earlier chaos at Trudeau airport, flight operations have since resumed, according to an airport spokesperson.

A spokesperson for the airport said a police tactical team set up a large security perimeter near the terminal at 10:35 a.m. so officers could analyze the package.  

Police said it was removed at around 1 p.m. and the contents were sent to a lab for tests.

"We didn't want to take any risk and any chances, because when there's an airport, there's a lot of people, so that's why we evacuated certain parts," said Montreal police spokesman, Const. Jean-Pierre Brabant.

At least 16 flights heading to U.S. destinations were unable to take off during the police operation earlier Sunday.

With files from Canadian Press