By Matthew Waller

MIDLAND, Texas (Reuters) - The four men killed when a freight train barreled into a parade float were identified as decorated U.S. veterans being honored for service in two wars, as investigators on Friday searched through wreckage in a West Texas oil town for clues to the cause of the accident.

Another 16 people were injured Thursday afternoon in the crash at the parade, which was the planned start of a weekend of events in Midland, Texas, saluting U.S. veterans of the Iraq and Afghanistan wars. Instead, a prayer service was held on Friday morning and a candlelight vigil was planned for Saturday night.

Police said the dead were Marine Chief Warrant Officer Gary Stouffer, 37; Army Sergeant Major Lawrence Boivin, 47; Army Sergeant Major William Lubbers, 43; and Army Sergeant Joshua Michael, 34.

Stouffer was on active duty and the other three were retired, according to biographies prepared for the events. Stouffer was waiting to see whether he could return to permanent limited duty or would receive a medical discharge.

Boivin's biography said he had been awarded the silver star and a purple heart; Lubbers' said he had been awarded the bronze star and purple heart; and Michael's that he had received the purple heart and was discharged due to brain injuries.

In Washington, the Army confirmed that Boivin and Lubbers were retired, but could not immediately confirm other details.

The National Transportation Safety Board sent 16 experts to the scene to examine evidence including video from a forward-facing recorder on the train, officials said.

Event recorders show the train was traveling at 62 mph, below the 70 mph speed limit, NTSB officials said. The agency will be checking to see what requirements there might have been for alerting the railroad about the parade.

The train's emergency brakes were applied before the crash, and the NTSB is trying to determine at what time and where. The investigation will also look into personal performance issues.

The NTSB said they plan to test the signals on Saturday to see if there were any problems. The automatic gate arm and one of the signal posts were destroyed in the crash, officials said.

SOME JUMPED FROM TRAILER

One person remained in critical condition and three were stable Friday afternoon at a Midland hospital, a spokesman said. Another person was in serious but stable condition at a Lubbock hospital. Eleven more were treated and released, police said.

The tragedy occurred as two flatbed trailers carrying the veterans, some of whom suffered major wounds in Iraq and Afghanistan, attempted to cross railroad tracks during the "Hunt for Heroes" parade.

The first flatbed crossed the train tracks completely, but the second had not cleared the tracks when the Union Pacific train reached the intersection. Continued...