DRENNEN, W.Va. (AP) — On Sunday, emergency crews planned to deploy an underwater drone in an effort to rescue a miner trapped within the depths of a submerged coal mine in West Virginia, officials reported.

The incident occurred when a mining team encountered an unexpected water pocket approximately three-quarters of a mile inside the Rolling Thunder mine near Drennen, situated around 50 miles (80 kilometers) east of Charleston, the state capital. This was revealed by Nicholas County Commissioner Garrett Cole through a Facebook update.

Following the incident, all other miners in the group were safely accounted for after the county emergency management department was alerted at about 1:30 p.m. on Saturday. The precise scale of flooding within the mine remains uncertain.

Governor Patrick Morrisey of West Virginia issued a statement explaining that the mine’s flooding resulted from the breach of an old mine wall. He confirmed that several state agencies have joined the operation, which includes efforts to pump water out of the affected area.

Rolling Thunder is part of a network of 11 underground mines managed in West Virginia by Alpha Metallurgical Resources Inc., a company based in Tennessee. Alpha also oversees four surface mines in the state, along with three underground and one surface mine in Virginia.

An engineering report conducted by Marshall Miller & Associates in February for Alpha highlighted that the mine’s area had undergone extensive exploration by previous owners. This exploration yielded a wealth of historical data, which Alpha utilized to evaluate the site’s coal production potential.

The same report says that the Rolling Thunder coal seam runs along and below the drainage of TwentyMile Creek, but said there were “no significant hydrologic concerns” about digging for more coal in the extensively mined property.