CLARENDON, Texas -- Investigators from the National Transportation Safety Board recovered event recorders -- the rail version of aviation's "black boxes" -- from two trains that collided head-on Tuesday near Clarendon, but a determination of the cause of the accident could take up to a year, the Amarillo Globe-News reports.

NTSB spokeswoman Lauren Peduzzi said Wednesday two investigators from the organization have been at the scene since Tuesday and are gathering information with the assistance of the Federal Railroad Administration and Burlington Northern Santa Fe. The information includes data from the event recorders, which will give the trains' throttle positions, braking and horn use.

"We're in the first part of our investigation, which is an intensive process of gathering information," Peduzzi said. "After the investigators have gathered as much information as they can at the site, they will start putting the information together and start doing analysis."

Peduzzi said an NTSB train crash investigation typically takes 9-16 months, after which a cause will be released.

The investigators are trying to determine what caused the two-train accident, which killed Galen Shelby of Lubbock and injured three others.

Two of the men who were injured, Bruce Patterson and Ronald Gordon, were listed in stable condition Wednesday at Northwest Texas Hospital in Amarillo, while the third, Rodney Torres, had been treated and released, according to hospital spokeswoman Caytie Martin.

Shelby and Gordon were the crew members on a westbound general freight train that collided head-on with an eastbound coal train crewed by Patterson and Torres about 9 a.m. three miles west of Clarendon.

As the investigation continued, BNSF workers were able to repair the damaged tracks and get trains moving once again on BNSF's main line through the area.

Joe Faust, regional director of public affairs for BNSF, said the final repairs to the damaged tracks were completed just before 6 a.m. Wednesday and the first trains rolled over soon after.

The track repairs are a small part of the cleanup effort.

Only one locomotive from the 30 derailed cars is salvageable, so the rest will have to be removed from the scene, Faust said.

Another part of the cleanup will include testing for environmental impacts. Faust said no hazardous materials were spilled in the crash, but BNSF is still cooperating with the Texas Natural Resource Conservation Commission and the Environmental Protection Agency to make sure no adverse environmental effects spring up from the crash.