A blast team supervisor is trapped underwater and feared dead after the ground gave way at a central Florida limerock mine.

Authorities say 35-year-old Kenneth Stephens Jr., of Beverly Hills, Fla., approached a lime pit Thursday after a routine blast at the Mazak Mine in Bushnell, about 50 miles northwest of Orlando. He was about 30 feet from the blast area when the ground gave way and he collapsed into the lime pit.

A pontoon boat has been lowered into the pit by a crane but rescue workers have been unable to find Stephens.

Rescuers plan to build a berm around the area and will begin trying to excavate the site.

Authorities say Stephens works for a subcontractor and had taken part in over 1,000 blasts.