A van loaded with vacationers on their way to Mexico rolled over on a highway southwest of San Antonio, killing two people and injuring 13 others, police said.

The right back tire of the 15-passenger van blew out and caused the 3 a.m. crash, said Lt. Steven Tellez, a spokesman for the Texas Department of Public Safety in San Antonio.

It wasn't clear how many of the 15 family members and friends from the Fort Worth area were wearing seat belts, he said.

The crash occurred on Interstate 35 about 30 miles southwest of San Antonio.

The van, which was headed south, veered left after the blowout and into the interstate's median, where it rolled over, Tellez said.

A 15-year-old boy and a 55-year-old man were killed, Tellez said.

All the injured were taken to a hospital. A hospital spokeswoman said she did not immediately know their conditions.