Officials have released the names of two workers trapped when a coal mine preparation plant collapsed earlier this week in eastern Kentucky.

Martin County Judge Executive Lon Lafferty identified the men as Billy Ray Daniels and Alvin Nees, news outlets report. Daniels died amid rescue efforts at the scene and Nees is believed to be trapped beneath the rubble. The men from neighboring Pike County were doing contracting work as part of the building’s demolition.

Lafferty said Thursday that the search for Nees is still a rescue operation.

Crews have begun removing layers of rubble and debris at the Martin Mine Prep Plant in Martin County where an 11-story abandoned building crashed down Tuesday night while undergoing work toward its demolition. Officials briefly made contact with Daniels, but announced Wednesday he died amid rescue efforts. Authorities said Thursday they have not had any communication with the second worker since the building collapsed at around 6:30 p.m. Tuesday in Inez, a town of about 500 people.

“We haven’t given up hope,” Lafferty said at a news conference with reporters Thursday.

Lafferty said a family member of the deceased man was at the site before he died and was able to speak with him. Crews have located his remains, but have not yet been able to remove them.

Crews delved under layers of steel and concrete with search dogs and listening devices Wednesday and Thursday, a line of emergency vehicles surrounding the wreckage of the once 11-story building, now flattened onto itself. In the second full day of rescue efforts, officials are removing the debris into smaller piles for the search, Lafferty said.

Several state agencies have begun investigations into the collapse and possible causes, including Kentucky state police.

The Kentucky Division of Occupational Safety and Health Compliance said one of its officers was on site and that an inspection had been opened with Lexington Coal Company LLC, which had contracted with Skeens Enterprises LLC for site demolition and salvage operations. The division said the investigation could take up to six months to complete.