A tour bus that crashed in Arkansas last week, killing 14 people, would have been pulled out of service had it been inspected before the fatal trip, investigators said.

According to the Associated Press, National Transportation Safety Board (NTSB) officials said they found pre-existing cracks on frame rails that held up the motor in the rear of the vehicle.

The NTSB did not link the cracks to the crash, and indicated that the cause of the accident remained under investigation. However, the cracks should have been discovered during an annual inspection and would have resulted in the bus being fixed before it was allowed on the road

Authorities do not know when the bus was last inspected.

Investigators also discovered that the roof of the vehicle had been altered, adding 600 to 700 pounds in weight to the bus. The NTSB has not stated whether this contributed to the accident.

The bus crashed on the morning of Oct. 9, along Interstate 55 about 25 miles north of Memphis, Tenn., when it failed to follow a left curve, careened off the roadway and flipped, killing the driver and 13 passengers.