PRAGUE (AP) — A passenger train collided head-on with a freight train in the Czech Republic, killing at least four people on board, officials said early Thursday.

At least 23 people were injured in the crash, Interior Minister Vít Rakušan said, adding that it took place late Wednesday night in the city of Pardubice, some 100 kilometers (62 miles) east of Prague.

The passenger train belonged to the private RegioJet company, Rakušan said.

Transport Minister Martin Kupka said a major track between Prague and the eastern part of the country had to be closed while authorities investigate the collision.

Prime Minister Petr Fiala called the crash a big tragedy and offered his condolences to the relatives of those killed.