MANILA - The Department of Energy (DOE) on Thursday said it is investigating a mudslide incident at a Semirara Mining and Power Corp. facility in Antique, where an employee is still missing.

In a statement, the DOE through its Energy Resources Development Bureau said it has immediately deployed a team of geologists and mining engineers to conduct on-site assessment.

Regular mining operations were ongoing on a drainage canal using a heavy machinery at the Molave Pit when an irregularity was detected at around 1 a.m. on Oct. 2. The mudslide occurred 5 minutes after at 1:05 a.m. hitting the heavy equipment and its operator, the DOE said, citing initial reports by Semirara.

The mudflow was confirmed at the site, the statement said.

"We are thoroughly investigating the matter to determine the cause of the incident, and ensure that all all safety standards and protocols were strictly upheld. The Semirara Mining Corporation has assured us of their full cooperation as we carefully look into the matter," Energy Secretary Alfonso Cusi said.

In a separate statement, Semirara on Thursday confirmed that the operator of a power shovel remains missing. The company said it would fully cooperate with the DOE's investigation.