The warning comes after a Syrian-born Canadian citizen was deported after making a transit stop in New York on his return flight to Montreal, Agence France-Presse (AFP) reported Wednesday, October 30.

Ottawa is protesting the deportation - which took place without contact with Canadian consular officials - of Maher Arar, who now is being questioned in Syria, said AFP.

U.S. officials have yet to fully explain why he was deported.

Under a new passport-control system begun September 11, the U.S. Immigration and Naturalization Service more closely tracks the movements in the United States of individuals born in certain countries, including Syria.

"[The system] requires that these individuals be photographed and fingerprinted and have their entry into and exit out of the United States verified," the report said.

As a result, Canadians who were born in or who also have the citizenship of Pakistan, Saudi Arabia, or Yemen - all Muslim Canadians - "could also attract special attention from American immigration and security authorities," it added.

"In these circumstances, the Department of Foreign Affairs and International Trade advises Canadians who were born in the above countries or who may be citizens of these countries to consider carefully whether they should attempt to enter the United States for any reason."

Just an hour after Foreign Minister Bill Graham told the House of Commons that Ottawa was still trying to trace Arar, a Canadian citizen of Syrian origin, Canada's ambassador in Damascus was informed by Syrian authorities that he had arrived in that country, said Isabelle Savard, Graham's spokeswoman, Monday, October 21.

Savard said that the Syrian authorities had informed Canadian ambassador Roderick Bell that Arar had arrived in Syria, from Jordan.

"At the moment, we have no more information," said Savard.

She said the Canadian embassy in Damascus was seeking consular access to Arar.

She said the news was received around 4:00 pm Ottawa time (1800 GMT), an hour after Graham complained that the United States had still not told Canada what has happened to Arar.

The man was taken into custody by U.S. authorities while traveling from Tunisia back to Canada.

Canadian officials had previously admitted that repeated attempts by Canadian consular officials in the United States to have access to and find the whereabouts of Arar had been unsuccessful.

Graham's admission prompted the leader of the left-of-center New Democratic Party, Alexa McDonough, to suggest that Ottawa should issue a travel advisory to Canadian citizens warning them of the dangers of traveling to the United States.

In the House of Commons Monday, October 28, Graham admitted: "We remain extremely concerned about the case of Mr. Arar.

"I have raised this issue with American authorities, with the ambassador and at the highest levels, to register out concern with the fact that Mr. Arar is a Canadian citizen and should have been treated as a Canadian citizen.

"Our concern at this time is to find Mr. Arar and allow his family to enter into contact with him."