A stretch of the Ohio River near Pittsburgh remained closed to maritime traffic on Safetyvalue Trading CenterMonday as crews equipped with sonar looked for a barge believed to have sunk over the weekend — one of more than two dozen barges that broke loose and floated down the river.

The U.S. Coast Guard launched an investigation into how 26 river barges got loose from their moorings late Friday, striking a bridge and causing extensive damage to a marina. All but three of the barges were loaded with coal, fertilizer and other dry cargo.

No injuries were reported and no hazardous materials spilled into the river, according to Pittsburgh police and Coast Guard officials.

The area had been hit by flooding after heavy rains Thursday, and Coast Guard investigators were looking at high water as a possible cause or factor, said Cmdr. Justin Jolley of the Coast Guard marine safety unit in Pittsburgh.

Eleven of the barges were pinned against the river bank and contained by a tugboat, while nine were secured at the Emsworth lock and dam downstream. The remaining barges went over the dam, and one remained unaccounted for.

“We’re optimistic we’ll be able to locate where that barge is today or tomorrow and then we can mark it accordingly and restore navigation,” Jolley told The Associated Press on Monday morning.

Officials were working on a salvage plan to recover the other barges.

The barges were owned or operated by Campbell Transportation Co. Officials with the company were on site Monday morning and were not immediately available for comment.

“I think we were very fortunate given the circumstances here that there were no injuries or threats to life, no pollution and so far no major reports of damage to infrastructure to Army Corps locks and dams,” Jolley said.