A transmission water main leak Friday afternoon caused a sinkhole off U.S. Highway 1 at Mile Marker 59, flooding the area and disrupting traffic.

The sinkhole appeared shortly after noon in the southbound shoulder at Mile Marker 59.5 and caused traffic congestion mostly along the southbound lanes, but did not create widespread traffic jams in either direction as motorists were being diverted around work crews, said Florida Highway Patrol Lt. Kathy McKinney.

A trooper was on the scene in case the situation worsened, McKinney said. There was no need to direct traffic as of 2:45 p.m., she added.

"We're just monitoring it at this point," McKinney said. "Traffic is just moving a little slower than normal."

The break in the 30-inch diameter pipe is causing customers from Grassy Key to Key West to experience reduced water pressure while crews make repairs, Florida Keys Aqueduct Authority Executive Director Kirk Zuelch said.

"It was definitely a major leak," Zuelch said.

Crews planned to work through the night to repair the leak, Zuelch said Friday.