An accident at an air shaft being built in a southern Indiana coal mine killed three people Friday, police said.

Detective Mike Hurt said the people died in a basket used to transport people up and down a 600-foot air shaft, but he could say whether they fell. Authorities did not believe there had been a cave-in or an explosion, he said, and no one else was believed to be injured or trapped.

Crews were working to remove the bodies at Gibson County Coal after the late-morning accident, Sgt. Jay Riley said.

Fire crews, police and the coroner were at the scene.

The mine, owned by Tulsa, Okla.-based Alliance Resource Partners, is northwest of Princeton, about 30 miles north of Evansville.

Julie Dozier, personnel coordinator at Gibson County Coal, confirmed the accident but offered few details.

Frontier-Kemper Constructors Inc. was working at the mine, designing and constructing a 550-foot-deep, 28-feet-wide service shaft, according to the Frontier-Kemper Web site.

The mine began production in July 2000. The last fatality was in November 2001, according to the U.S. Mine Safety and Health Administration. The miner died after being pinned by equipment, and operator error was cited as the cause of the accident.

In 2006, the company produced more than 3.5 million tons of coal, ranking second among the state's coal producers, according to the Indiana Coal Council.