Const. Ian MacDonald says an officer observed the vehicle travelling at least 40 kilometres below the speed limit at about 7 p.m. Friday along the Canada-U.S. border in the Sumas Prairie area.
He says the officer also noticed at least two of the men wearing camouflaged clothing.
MacDonald says the Canadians — a couple in their 50s from Burnaby — have been released as the investigation continues.
The Mexican men, who are in their 30s, have been detained for immigration purposes.
Along with the vacuum-packed U.S. currency, MacDonald says police also seized up to $4,000 in Canadian cash.
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