YUMA - Smugglers who abandoned two truckloads of marijuana along the Colorado River after crossing into the United States fired shots at a helicopter carrying federal agents, but missed, authorities said.

Authorities monitoring remote surveillance video cameras along the river spotted six vehicles cross the river from Mexico into Arizona late Monday night.

The smugglers drove back toward Mexico when Border Patrol agents approached. But two of the smugglers' vehicles got bogged down in the sand, and those who were in the disabled trucks escaped on foot.

As a U.S. Customs and Border Protection helicopter carrying Border Patrol and CBP agents flew nearby to help agents on the ground, a number of shots were fired at the aircraft, apparently from across the river, agents said.

The Border Patrol said neither agents nor the chopper were hit and that the pilot moved the aircraft to safety.

Agents seized 175 bundles of marijuana that weighed almost 2,300 pounds from the two vehicles that were left behind. The pot has an estimated street value of more than $1.8 million, the Border Patrol said.

Both vehicles had been reported stolen.