Ottawa recently put airlines and carriers on high alert following a series of security warnings in the wake of the failed Christmas Day terror attack, Transport Minister John Baird confirmed Tuesday.

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.

"We don't want panic. At the same time I think the public would expect us, when there's a reasonable concern, to be open and honest about that heightened concern."

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 a Northwest Airlines flight on Dec. 25.

Transport Canada spokesperson Maryse Durette emailed CTV.ca a copy of a security notice she said was issued Saturday:

"In light of the incident on Northwest flight 253 on Christmas Day and the continued investigation thereof, Transport Canada requests that all air carriers, aerodrome operators and CATSA screening officers continue to exercise increased vigilance and strict adherence to all aviation security requirements.

The Government of Canada takes this matter very seriously and, at this point, the Department is satisfied that the additional security measures implemented since December 26, 2009 are appropriate to mitigate the identified threat.

The Department asks that you continue your efforts to ensure the security of the aviation system.

Your cooperation is appreciated."

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.

Fife said Canada has long suffered from the mistaken perception that the Sept. 11 terrorists had entered the United States from its neighbour to the north.

"We're still really not over it," Fife said, pointing to erroneous statements from senior U.S. politicians in recent years.

"It's a big perception problem for Canada," he added.

Canadian airports tightened security following the unsuccessful attempt to blow up the Detroit-bound airliner, allegedly through explosive materials hidden in the underwear of Umar Farouk Abdulmutallab -- a 23-year-old Nigerian national who has been arraigned on six criminal charges in the United States. He has pleaded not guilty to the charges.

Ottawa plans to install 44 body scanners that can see through clothing at airports across Canada. The $250,000 will be used to identify suspicious passengers who will then face further screening.

Jim Facette, the president and CEO of the Canadian Airports Council, said it is advisable for air passengers to familiarize themselves with what is expected when going through security.

"I think the first thing you do is inform yourself about what is and is not allowed on board the airplane, pack as light as you possibly can and come to the airport with a sufficient amount of time -- two to three hours in advance on a trans-border flight," he told CTV News Channel from Ottawa.

With files from The Canadian Press