LOUISVILLE, Ky. (WDRB) -- Indiana State Police say "driver error" is to blame for the bus crash that injured members of a college bowling team last month.

The crash occurred March 12 at the southbound rest area on Interstate 65, near Henryville in Clark County.

State police said the bus driver, Rex Altenburg, 76, of Fort Wayne, Ind., drove the bus off the left side of the road "for an unknown reason" and overturned. Investigators could not attribute any medical or physical conditions, a state police news release said.

Officers also said mechanical issues were not a factor in the crash.

The driver and twenty members of the Indiana Tech bowling team were hurt. They were en route to a bowling tournament in Smyrna, Tenn., school officials said.

Most of the injured were treated and released from area hospitals the day of the crash; however the driver and some passengers remained in the hospital for several days.

State police said investigators found the bus was traveling at the 70 m.p.h. speed limit in the minutes before the crash. However, they were not able to glean additional information about the cause of the crash from electronic data and video recordings. A video recorder stopped working about two miles before the scene of crash, a state police release said.

The investigation also found no mechanical problems with the bus, police said.

Read the complete state police news release below:

"The investigation into the March 12, 2015 charter bus crash on I-65 has concluded with investigators saying driver error was to blame for the crash which sent 20 passengers and the driver to local hospitals. The charter bus was carrying 16 members of the Indiana Institute of Technology (Indiana Tech) men's and women's bowling team to Smyrna, Tennessee to compete in a United States Bowling Congress Sectional Competition when it overturned near Henryville, Indiana. Most of the passengers were released from the hospital on the day of the crash; however, the driver and a few passengers remained hospitalized for several days before being released.

"The investigation included interviewing bus passengers and witnesses but also included more in-depth procedures such as attempting to gain information from the Event Data Recorder (EDR), as well physical inspection of the bus by Commercial Motor Vehicle Enforcement officers, and computerized photographic reconstruction of the scene by crash reconstructionists. The investigation lasted approximately three weeks.

"Investigators were hopeful that onboard recording equipment would also shed light on to the cause of the crash; however, the camera stopped recording approximately two miles before the scene of the crash. The pre-crash recording did not reveal any unusual driving behavior but did confirm that the bus was traveling the posted 70 mph speed limit. To date, attempts to gain information from the Event Data Recorder have also been unsuccessful. A physical inspection revealed no mechanical issues with the bus.

Taking all available data into account, investigators said the driver, Rex Altenburg, 76, Fort Wayne, Indiana, drove the bus off the left side of the roadway for an unknown reason. No medical or physical conditions have been attributed to his actions. Investigators said the driver then over-corrected, putting the bus into a lateral skid back across both southbound lanes of the interstate. The charter bus rotated clockwise and was facing north before traveling off the east side of I-65. The bus overturned after striking a rocky ditch line approximately 36 feet off the east side of the roadway."

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