CREIGHTON — Officials fear that an underground coal refuse fire may be spreading.

Workers say fire was seen shooting up through the ground behind the Pittsburgh Glass Works plant in East Deer Township Thursday, a Pittsburgh newspaper reported.

PGW, the current owner, “discovered visual embers and flame in a small crack in the soil about 30 or 40 yards away from its auto glass production building.” The crack was about 6 feet in length and 3 inches wide,” the company said in a statement.

Since last September, the company has been investigating an ongoing fire under the plant caused by coal refuse apparently used as backfill years ago.

Officials say workers suppressed the flames and are clearing vegetation from the area. Air quality will be monitored inside the plant, where the company has had to address localized hot spots on the concrete floor.

Operations at the 135-year-old automotive glass manufacturing site formerly owned by PPG are to end as production is moved elsewhere.