A report by the GAO raised questions about potential security gaps along the 4,000-mile border between the U.S. and Canada, with analysts saying the "risk of terrorist activity is high," though the extent of any such activity is unknown.

The GAO report focused its review on four of the 13 northern border sectors, including the Detroit sector's 863 miles of water border. GAO researchers described the potential threat challenging security officials in Detroit as "criminal organizations including terrorists, and those that smuggle drugs and people via recreational vessels." The report did not quantify the threat. And overall, the report found that only a small percentage of the northern border was secured appropriately.

Read the full report here http://www.gao.gov/products/GAO-11-97