MEXICO CITY (AP) — Armed thieves tried to abduct an entire convoy of fuel tanker trucks in northern Mexico, but security forces fought off the gang in a shootout.

Mexico began moving fuel in tanker trucks this year to combat thefts from government pipelines. But now thieves appear to be attacking even fuel convoys.

Prosecutors in the northern border state of Sonora said Tuesday that two police officers noticed several fuel tanker trucks pulled over on the side of a highway. The trucks were carrying fuel to nearby mines.

Two gunmen who had apparently hijacked the convoy opened fire on police, wounding one of them.

An army squad later moved in to help pursue the gunmen, who fled, leaving behind an assault rifle, a pickup and fuel containers.