BOGOTA, Colombia (AP) — Search and rescue personnel on Saturday finished recovering the bodies of a group of miners who were trapped earlier this week inside an informal coal mine following a methane gas explosion.

The country’s mining regulatory agency announced on social media that four bodies were recovered Saturday. Two others had been found a day earlier and turned over to the Colombian Attorney General’s Office’s investigative unit.

Authorities have said Thursday’s explosion was caused by a methane gas buildup at the Mata Siete mine in Guacheta, about 75 miles (120 kilometers) north of the capital, Bogota, a region where coal mines are prevalent.

The National Mining Agency previously said the Mata Siete mine operated with an “expired mining permit” and engaged in “illegal coal mining.” It also received a closure order in March 2019.

The agency said the explosion remains under investigation.