A large fire has broken out at refugee camp in Slovenia with firefighters trying to put it out and Slovenian riot police in full gear on standby. More than 1,000 migrants were dropped at the Slovenian border by train from Croatia early Wednesday.

It’s not yet clear what caused the fire at the camp located in Brezice near the Slovenian border with Croatia. A report on Twitter claimed refugees set fire to tents.

However, AP reported that a many refugees have been lighting fires to keep warm in the cold weather.

Emergency workers have been helping those at the camp, with riot police managing the situation as fire and smoke spread through the camp. Ambulances have also been spotted at the scene.