Seven people were killed and at least five more injured when an international train and a bus collided in southwestern Slovakia on Thursday afternoon, the country’s emergency services said.

The cause of the crash remains unclear and investigation is ongoing, according to the emergency services.

Those who died are believed to have been on the bus. Slovak national railway company ZSSK said on a statement on Facebook that none of the more than 100 passengers on the EuroCity train died as it sent its condolences to “the families and loved ones of the bus passengers who were injured or lost in this accident.”

The emergency response continued into the night at the crash site in Nové Zámky, southern Slovakia, the Slovak Emergency Medical Service said. Five ambulance vehicles and three ambulance helicopters are on the scene.

Reuters footage from the scene showed smoke and fire billowing from a train carriage, with a person in the background heard saying: “There was just a big bang. Then the train stopped. We were able to get off, but the whole front part of the train was burning.”

The train was traveling from the Czech capital of Prague to the Hungarian capital of Budapest. More than 100 of its stranded passengers were transported by buses to the town of Sturovo on the Hungarian border.