OTTAWA—A newly declassified report says smugglers were caught trying to slip dramatically more people into Canada from the United States in 2011 compared with the year before.

The binational report on border security says authorities apprehended 487 people as smugglers attempted to sneak them into Canada at unguarded points along the border — a 58 per cent increase over 2010.

At the same time, the number of people caught being spirited into the U.S. from Canada fell slightly during the same period to 360.

The figures on smuggling activity between official ports of entry appear in the 2012 Integrated Border Enforcement Team threat assessment report, obtained by The Canadian Press under the Access to Information Act.

An advocacy group for refugees attributes the surge in Canada-bound human smuggling attempts to an agreement between the countries that has prompted desperate refugees to turn to criminal groups willing to help them across the border.

Under the Safe Third Country agreement, which took effect in December 2004, Canada and the U.S. recognize each other as safe places for refugee claimants to seek protection.