Luminant Mining Co. is laying off 80 workers as it closes three Northeast Texas coal mines, company and workforce officials said Monday.

The layoffs are set to take effect April 29 at Luminant's Winfield Mine in Titus County, its Monticello Mine south of Mount Pleasant and its Thermo Mine near Sulphur Springs in Hopkins County.

Luminant announced in 2014 that mining operations would end at those sites, company spokesman Brad Watson said Monday.

Operations at Monticello Power Plant southwest of Mount Pleasant will not be affected by closure of the nearby mines, he said. The plant will be fueled by Powder River Basin coal, which is available year-round at all three Monticello units.

"The decision to close the mines was made based on the current business climate and not as a response to current or pending environmental regulations," Watson said.

Here are the layoffs by location, according to required filings with the Texas Workforce Commission:

Winfield: 29

Sulphur Springs: 26

Mount Pleasant: 27

In September, Luminant said it was closing a mine outside Beckville early this year and moving workers to other area mines that serve the Martin Lake plant in Rusk County.

"Beckville Mine is nearing the end of its lignite production," a company spokeswoman said at the time.

The 90 or so employees of that mine were being moved to mines near Liberty, Oak Hill and Tatum.