In the wake of a failed attempt to blow up a Northwest Airlines flight on Dec. 25, airports across North America ramped up their security measures.

Yet, on a visit to Vancouver International Airport on Tuesday, CTV News found what appears to be a security gap.

Along a stretch of the airport's perimeter fencing, there was a hole wide enough for someone to easily climb through and into a restricted area.

Just last month, a valet driver accidentally drove an SUV deep into the international terminal at YVR.

YVR officials refused to speak on camera Tuesday, instead opting to send CTV News an email, which stated:

"We have a very strong security plan in place that is constantly updated. As you can appreciate, we cannot divulge details about it.... I can assure you that the locations identified ... are part of that plan.

"The security of the travelling public takes precedence over our policy of open and transparent communication with the media."

Security expert Andre Gerolymatos said airport officials should be communicating to the media what security measures they are taking because that could be a deterrent to potential terrorists.

"They shouldn't keep it secret. Security is everyone's concern, not just YVR's," he said.

Heightened alert

Transport Minister John Baird confirmed Tuesday that Ottawa recently put airlines and carriers on high alert following a series of security warnings.

The transport minister said the "medium level" warnings the government had received were not imminent, though he called on Canadians to be vigilant when travelling by air.

"There's specific information that certainly causes me concern, causes our security officials concern, and I think we need to maintain heightened vigilance in this time," Baird told reporters in Toronto.

Baird did not provide specific descriptions of the threats when speaking to reporters.

On Saturday, Transport Canada sent a memo to air carriers, airports and security personnel advising them to "exercise increased vigilance and strictly adhere to all aviation security requirements" -- including the new protocols that were ushered in after the failed attempt to blow up the Northwest Airlines flight.

As CTV News reported late Monday, the Transport Canada security notice was sent out after intelligence reports suggested terrorists are planning to enter Canada, purportedly so they can make their way to the United States.

This prompted a meeting that involved Prime Minister Stephen Harper and his national security ministers on Monday.

CTV's Ottawa Bureau Chief, Robert Fife, told CTV's Canada AM that one of the reports came from British and U.S. intelligence sources and suggested 20 Yemeni-trained terrorists are "trying to get into North America."

Separately, Canadian intelligence officials "gathered credible evidence that there was another group of terrorists who were also trying to get into Canada," he said.

Canadian officials believe that terrorists are ultimately interested in entering the United States and that they do not have Canadian targets in mind, Fife said.

Peter St. John, an airport security expert, said Tuesday the public can't rely solely on airports to ensure security.

"A lot of good airport security can be helped by the public being vigilant and sensible and I find our travelling public to be very sensible and quite observant, sometimes more observant than our security systems," he said.

With a report from CTV British Columbia's Lisa Rossington and CTV.ca News