3 Injured at Western Pennsylvania Stone Quarry

Three workers were hurt, two seriously, after ground shifted at an underground limestone mine in western Pennsylvania causing a rush of air through the mine's entrance, near where the men were found.

The workers were about to enter the Whitney quarry in Unity Township, Westmoreland County when they were hurt about 5 a.m. Wednesday, said Amy Louviere, spokeswoman for the U.S. Mine Safety and Health Administration.

The company and MSHA investigators couldn't immediately characterize what happened as a collapse because they have been unable to enter the underground portion of the site.

The miners were found about 50 feet from the entrance. Two who were unconscious were flown to Pittsburgh hospitals and the third was taken by ambulance to a hospital closer to the mine, Louviere said. The mine is about 40 miles southeast of Pittsburgh.

The mine is run by Hanson Aggregates. But that company, in turn, is part of Lehigh Hanson Inc. of Irving, Texas, which is part of HeidelbergCement Group.

Lehigh Hanson spokesman Jeff Sieg said company officials weren't sure exactly what injured the workers. Whatever ground fell into the mine caused air to rush out of its entrance, much like pressing on a balloon would cause air to rush out of its opening, Sieg said.

As a result, company officials weren't sure if the workers were knocked down or thrown by the force of the air, or whether they were hit by debris, or both. Nobody was in the mine at the time.

The names and conditions of the workers were not immediately released.

The companies pledged to work with MSHA to "ensure a thorough investigation,'' according to a statement.

MSHA records show 10 miners have been hurt at the quarry in the last 11 years, none fatally. The last was in 2011 when a worker's finger was broken when wind blew the door of a piece of heavy equipment shut.