(CNN) -- Three construction workers replacing an air shaft at a southwestern Indiana coal mine were killed in an accident Friday, authorities said.
Three construction workers were killed in an accident Friday at an Indiana coal mine, police said.
The incident happened around 11 a.m. CT (noon ET) at a mine operated by Gibson County Coal Co., police said.
"We're not sure if it was an equipment problem or what at this point," said Mike Hurt of the Princeton, Indiana, police department.
Work to replace the air shaft at the face of the mine was going on at the time of the accident, said mine superintendent Jim Browne.
The workers were employed by Frontier-Kemper Constructors Inc. of Evansville, Indiana. Watch initial reports of the deadly accident »
Crews are working to retrieve the bodies from the mine, an underground complex just north of Evansville, Hurt said.
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