According to the report, the accident killed four people, with 21 passengers having been injured.
For unknown reasons, the driver of a bus with Ukrainian plate numbers going towards Warsaw drove onto the contraflow lane, flew into a ditch and hit a tree. The bus was carrying about 50 people.
The rescue operation involved 15 fire vehicles, two air ambulance helicopters, 11 ambulances from nearby hospitals.
Investigation into the accident is underway. According to Polish media, the bus driver was sober.