Importing cheaper prescription drugs should not come at the expense of safety, said a U.S. government report issued on Tuesday that highlighted the problems of ensuring the medicines are equivalent to those in the United States.

Congress required the Health and Human Services Department to conduct the study under last year’s Medicare modernization law to see if a federal system could safely import medicines.

Many Americans, particularly those with limited incomes who live close to the Canadian and Mexican borders, have been visiting those countries to obtain prescription drugs. Internet sites have also touted cheaper imported medicines.

But the report by top U.S. health officials said the increasing volume of imported drugs made it difficult to ensure safety.

Surgeon General Richard Carmona, a member of the task force that produced the report, told reporters the group had made no recommendation on importation.

“Debates are the purview of Congress…We’ll go as far as the facts lead us,” Carmona said during a conference call.

The officials, who also included Acting FDA Commissioner Lester Crawford and Medicare chief Mark McClellan, were particularly concerned about the safety of drugs requiring special refrigerated handling, or those susceptible to counterfeiting.

They said Americans who travel to Canada and purchase drugs from regulated pharmacies “may very well get drugs that are fully regulated.” But Internet shoppers were more vulnerable.

“Practical experience and evidence shows that Americans are not always getting the same drugs as Canadian citizens when purchasing drugs from Canadian Internet sites or sites purporting to be Canadian,” the report said.

Several states and cities, including Wisconsin, Illinois, and Springfield, Massachusetts, have arranged for imported medicines or directed residents to online Canadian pharmacies.

Canadian officials have warned their country cannot act as America’s drugstore for fear of drug shortages.