AUSTIN, Texas (Reuters) - At least 13 people were killed, and two injured, when a Texas church bus carrying senior citizens collided head-on with another vehicle on Wednesday, the church and a Texas state trooper said.

The bus had 14 people aboard when it collided with a pickup truck carrying one person, about 80 miles (130 km) west of San Antonio. The cause of the crash was being investigated, said Sergeant Conrad Hein, a spokesman of the Texas Department of Public Safety.

The vehicles collided when the truck crossed the center line, Johnny Hernandez, a spokesman for the Texas Department of Public Safety, told the San Antonio Express-News.

The truck driver was airlifted to a San Antonio hospital, the paper said on its website. The survivor who was on the bus was in serious but stable condition, the First Baptist Church of New Braunfels said on social media.

A group of senior adults affiliated with the church were on the bus returning from a three-day retreat in Leakey, Texas, the church said on its Facebook page.

“Thank you for the outpouring of love and support,” it added. “Please continue to pray.”

Texas Governor Greg Abbott and his wife offered condolences to the victims.

“We are saddened by the loss of life and our hearts go out to all those affected,” Abbott said in a statement.