An SUV crammed with at least 15 people rolled during a police chase in South Texas early Thursday, leaving six people dead and seven more injured, police said.

Police are trying to determine who was driving the 2003 Ford Explorer when it crashed in Edna, about 90 miles southwest of Houston. Two people who ran from the scene were tracked down and detained, police Chief Clinton Wooldridge said.

Authorities are trying to identify the victims, some of whom came from Honduras and Guatemala, Wooldridge said. He had no information on their legal status, but said the vehicle seemed to have been adapted to fit in many passengers, hinting at the possibility of a people-trafficking operation.

"Officers noted that the rear seat in the vehicle had been folded down and the middle seat had previously been removed, apparently to create more room in the vehicle," Wooldridge said.

Wooldridge said the two people who ran are now in the custody of immigration officials.

Five patients who were treated at Jackson County Hospital in Edna have been released to the custody of U.S. Border Patrol agents, hospital spokeswoman Donna Coleman said. She said two others are at a hospital in nearby Victoria in stable condition.

Leticia Zamarripa, a spokeswoman for U.S. Immigration and Customs Enforcement, said she was still gathering information on her agency's involvement in the case.

Officers tried to stop the SUV for a traffic violation but the vehicle sped away and police gave chase. As the vehicle veered onto Highway 59, the driver seemed to overcorrect and the SUV flipped several times, police said.

Four people died at the scene and two more died at hospitals, Wooldridge said.

It is not uncommon for vehicles packed with immigrants who have entered the U.S. illegally to be involved in deadly crashes as they are shuttled away from the border.

Last year, a South Texas teenager was sentenced to 20 years in prison after being convicted in a 2012 accident that killed nine immigrants. The teenager had been fleeing Border Patrol agents when the van he was driving with at least 17 immigrants inside flipped. Also, a Mexican man was sentenced to 45 years in prison over a crash that left seven immigrants dead in 2013.