SEATTLE - A gravel barge that broke in half Friday afternoon off Harbor Island has been towed away from the scene.

Officials said there was no pollution from the mishap, but the incident remains under investigation. The barge was towed across the Duwamish Waterway to Terminal 105.

The Coast Guard says the barge broke in half while being loaded with gravel Friday and settled in shallow water off Harbor Island.

Lt. Jennifer Runion said the barge spilled gravel into the water and sent shock waves around Harbor Island.

"I thought I felt an earthquake," said a man named Ed who was working on his boat at the time.

"We're just down working on the boat and next I know, we're being thrown around on the boat, huge waves coming through here," said Mike Leary, who was also nearby.

Runion says one man was on board the barge at the time but was not injured.

Runion says no reports of contamination have been received. Coast Guard investigators will assess any ecological effect.

A front-end loader was taken off the barge to prevent it from falling in the Duwamish Waterway and releasing oil into the water. The barge did spill some gravel, however, prompting crews to organize a cleanup effort.

Runion says the 273-foot barge was loading at the Ash Grove Cement Co. terminal on Harbor Island.

The cause of the incident is not known. State officials are working with the Coast Guard to review inspection records and to make sure all proper procedures were followed.

"It's always concerning when a vessel buckles like that, or a barge buckles like that. It's not supposed to happen," said Petty Officer Michael Donaldson with the U.S. Coast Guard.

The barge is owned by Island Tug and Barge.