UVALDE, Texas (AP) - Federal investigators are getting their first look Thursday at the scene of a head-on collision involving a small church bus and a pickup truck that killed 13 senior adult church members onboard the bus.The Texas Department of Public Safety reported the lone bus survivor remains hospitalized in critical condition, and the pickup truck driver is in stable condition.The National Transportation Safety Board sent investigators to the scene to begin seeking the cause of the crash, NTSB spokesman Terry Williams said Wednesday.Twelve bus occupants, including the driver, were dead at the scene of Wednesday's crash, DPS Lt. Johnny Hernandez said. One bus passenger died later at a San Antonio hospital.The wreck happened about 12:30 p.m. on U.S. 83, a two-lane highway, outside Garner State Park in northern Uvalde County. The area is about 75 miles (120.7 km) west of San Antonio.It was not immediately clear what caused the collision about 120 miles (193.1 km) from the church, where the members were headed.Photos and video of the crash's aftermath showed heavy damage to the front drivers' sides of both vehicles where it appeared the two had collided. The back of the bus was up on a guardrail, with glass and debris scattered onto the grass below.Hein said the small bus was a 2004 Turtle Top, though he did not know the specific model. Turtle Top's website features shuttle buses with capacities ranging from 17 to 51 passengers, which they bill as 'a great alternative to the standard 15-passenger van.' Safety concerns have long surrounded the 15-passenger vans, also frequently used by churches and other groups, with advocates saying they can be difficult to control in an emergency.Church officials said in a statement on the First Baptist website that the members were returning from a three-day retreat at the Alto Frio Baptist Encampment in Leakey, about 9 miles (14.5 km) north of where the crash happened.The church officials were 'ministering to family members to help them deal with this tragedy,' according to the statement. Counselors also were scheduled to be available Thursday at the church.Texas Gov. Greg Abbott and his wife, Cecilia, offered their condolences in the hours after the crash.'We are saddened by the loss of life and our hearts go out to all those affected,' their statement said. 'We thank the first responders working on the scene in the wake of this unimaginable tragedy, and ask that all Texans join us in offering their thoughts and prayers.