SKOPJE, North Macedonia (AP) — Two Bulgarian military planes landed in North Macedonia Friday to return the remains of 45 people killed in a bus crash in Bulgaria last month to their families for burial.

The bus had been carrying 52 people, mostly from North Macedonia and including 12 children, and the accident occurred as it was returning from a trip to Istanbul, Turkey, on Nov. 23. It smashed into a highway guardrail in western Bulgaria and caught fire, and the bus's blocked exits prevented the people on board from escaping.

North Macedonia's authorities had planned a procession to honor the dead in the capital Skopje. But the event was canceled at the request of the victims’ families so that Muslims among the dead could be buried before Friday prayers in accordance with religious tradition.

The country’s top officials and religious leaders attended a brief ceremony at Skopje International Airport. The coffins, wrapped in clear plastic, were placed by military personnel into vehicles bound for burial sites.

Bulgarian authorities have not yet announced the results of an investigation into the cause of the accident, but prosecutors say early indications suggest human error. Seven people survived the crash: five citizens of North Macedonia, one Serb and one Belgian.

Authorities in North Macedonia have revoked the license for the travel company that organized the trip. Two customs officers were also suspended due to insufficient border checks.