Undercover American investigators who snuck duffel bags across the U.S.-Canada border have concluded that a smuggler could easily carry radioactive material or other contraband from one country to the other.

As of May, fewer than 1,000 U.S. Border Patrol agents were keeping watch over the Canadian border.
(CBC)

The Government Accountability Office, an investigative branch of the U.S. Congress, sent out investigators to test how difficult it would be to transfer large red duffel bags at unguarded and unmonitored spots along the 8,000-kilometre border.

The tests were conducted from four northern states, which were not identified. The exercises were videotaped and photographed.

During one of the tests, a citizen noticed the unusual activity and alerted a border official, but by the time authorities arrived, they could not locate the undercover investigators.

"Our work shows that a determined cross-border violator would likely be able to bring radioactive materials or other contraband undetected into the United States by crossing the U.S.-Canada border at any of the locations we investigated," the GAO report states.

The details of the investigation were outlined in a 13-page report that was given to Congress on Thursday.

"It's extremely troubling," said New York Senator Chuck Schumer during a Senate hearing into the report's findings.

'Obviously, we have to be concerned': Harper

Investigators determined that the Canadian border with the United States "presents more of a challenge" than the U.S.-Mexico border.

When asked Thursday about the report, Prime Minister Stephen Harper said his government has made significant investments in border security through increasing the number of border guards and boosting co-operation with their U.S. counterparts.

"As you know, the particular materials were admitted through American security on the American side of the border," the prime minister told reporters.

"But obviously, we have to be concerned. We work hand in glove with American authorities dealing with any kind of threats."

Public Safety Minister Stockwell Day said the U.S. senators were sincere, but uninformed. He said Canada has an aggressive program when it comes to terrorism, but that no country can be immune to it.

The report notes that as of May, there were only 972 U.S. Border Patrol agents on the Canadian border, while 11,986 agents patrolled the Mexican border.

Investigators examined the southern border and said they observed a significant number of U.S. National Guard troops and U.S. Border Patrol personnel while driving on state roads, but found little law-enforcement presence on vast stretches of surrounding lands managed by the U.S. government.

Investigators said for security reasons they did not conduct the duffel bag tests at the U.S.-Mexico border.

It is illegal to cross the border at any place other than an official port of entry.

With files from the Associated Press