The Oranovo coal mine near the town of Simitli in southwest Bulgaria collapsed Tuesday morning, according to the Associated Press.

The entrance to the mine is blocked, but a rescue team is working to provide the mine with fresh air as they remove rocks to reach the two trapped miners.

Local fire chief Georgi Parmakov confirmed on Tuesday that the bodies of the two other miners were recovered.

Union leaders are blaming poor safety for the collapse. It is the fourth major accident at the mine in eight years.

Mine management has not yet issued a statement.