SKOPJE, North Macedonia (AP) — A public prosecutor's office in North Macedonia says six people have been detained following a preliminary investigation into a bus crash that killed 15 people and seriously injured 39 others.

The office said Thursday that the suspects include the bus driver and owner of the private transportation company. They were detained on suspicion of gross negligence, endangering public safety and other offences. The charges carry a combined penalty of up to 10 years in prison.

In the Feb. 13 accident, the bus carrying mostly students and office workers from Skopje to the western town of Gostivar drove off the highway embankment and overturned.

A spokesman for the prosecutor's office said the preliminary investigation had found evidence that the bus had exceeded the speed limit and had a defective braking system.