A transformer explosion that caused a fire in a coal mine in western Turkey on Wednesday killed at least 201 workers. The accident is considered one of the worst mining disasters in the country's history.

According to Turkish Energy Minister Taner Yildz, 787 miners were inside the coal mine in Soma, located 155 miles south of Istanbul. So far, 363 workers have been rescued, while more than 200 are still trapped.

He said at least 80 miners are injured, four of whom are in serious condition.

The incident happened when the miners were preparing to change shifts. Since there were more workers inside than usual, officials warned the death toll could be higher than the initial number of 201.

Yildiz said the 201 died by carbon monoxide poisoning.

The Natural Disaster and Emergency Coordination Directorate said the mine shaft is about two-thirds of a mile or 1 kilometre underground. The directorate has sent about 100 rescuers, dozens of ambulances and a helicopter to the mine for search-and-rescue operations.