The Canadian government issued a call on Thursday for tenders for construction of temporary winterized housing, prompting speculation it will build refugee camps to handle the arrival of 25,000 Syrian refugees before year end.

In a public tender, Public Works Canada said it was looking for companies with the capacity to build "temporary winterized lodgings for groups of 500 to 3,000 people by early December 2015 at sites to be confirmed."

The notice said the housing and services may be required for up to three months and that the sites must be self-contained and self-sustaining, including on-site energy, water, sewage and waste management.

Government officials had no immediate comment. At least four potential bidders said they believed the project involved refugee housing.

There are no refugee camps in Canada. Immigration detention centers, similar to jails, are used during deportation, to guard against flight risk, or for temporary use by border agents during legal procedures. Refugees otherwise have freedom of movement.

One U.S. official said his understanding was that once the refugees arrived in Canada, authorities would detain them in some kind of "camp" and not release them until after a thorough vetting.

Another U.S. security official said that far as he knew, Canada and the United States were still using identical vetting procedures for Syrian refugees, which normally take 18 to 24 months.

Canada has said most of the security vetting for the refugees will be done before they arrive. But to meet Prime Minister Justin Trudeau's Jan 1. deadline, some screening will have to be done after they arrive in Canada.