Police in Texas say at least 13 people are dead and 12 others injured after a crowded pickup truck slammed into a tree along a rural highway.

Authorities investigating Sunday's crash near Berclair, about 130 kilometers south of San Antonio, said they believe most of the victims were illegal immigrants.

Border Patrol officials are assisting with the probe into the accident. Authorities say about two dozen people were crammed into the truck at the time.

In April, a van carrying immigrants crashed while fleeing Border Patrol agents near the Mexican border, killing nine of the 17 people on board.