WARSAW, Poland (AP) — A Warsaw city bus crashed through a barrier on a highway overpass on Thursday and fell onto a concrete embankment below, killing at least one person and injuring about 20 others, authorities said.

Five of the injured people were hospitalized in serious condition, Health Minister Lukasz Szumowski said.

Warsaw Mayor Rafal Trzaskowski, a candidate in a weekend presidential election, suspended his campaigning outside of the capital and went to the scene of the crash.

The articulated bus appeared to split in half, with the front section resting on its side on the embankment after it slammed through the barrier and plunged several meters below. The back of the bus was left dangling above on the railings with a gaping tear in the middle section.

Trzaskowski said investigators believe the bus driver might have lost control after suddenly becoming weak, but warned that the investigation was still ongoing. He said the driver was young and the bus was a year old.

The driver was hospitalized, but wasn't in serious condition, police said.