AUSTIN, Texas -- Three employees of a company that inspected the chartered bus involved in a deadly wreck in Sherman last year are accused of not properly checking vehicles. The Department of Public Safety on Monday announced charges against three workers at 5 Minute Inspections in Houston. The men, following a three-week DPS investigation, were charged with tampering with a government document.

In August 2008, a bus loaded with Vietnamese Catholics crashed on the way to Marian Days in Carthage, Mo. Seventeen people died.

Police in Sherman, Texas, have already revealed that the driver had used cocaine before the trip. He wasn't charged with a crime because the drug was not in blood samples but he could be fined.

The National Transportation Safety Board also found the Texas-based bus company was operating illegally because its vehicles had not passed federal safety inspections.

The manager on duty Monday at 5 Minute Inspections refused to provide his name to a reporter and declined comment. DPS says the company is certified to inspect passenger and commercial vehicles but investigators believe it issued hundreds of stickers a month on vehicles not inspected.

DPS did not provide details on whether the bus in the wreck that left 17 dead was properly checked by 5 Minute Inspections, saying the investigation continues.