The Mathews Bridge will be closed to traffic for several days after a Navy transport ship being towed by tug boats, struck the span of the bridge, knocking loose a steel support beam.

Late Thursday afternoon, the Jacksonville Sheriff's Office announced the bridge that 56,000 vehicles cross every day will be "closed indefinitely."

"This will be the most significant delay the city has seen in a long time," JSO Assistant Chief Leonard Propper said.

The Florida Department of Transportation was assessing the extent of the structural damage.

"The part of the bridge that gives the weight support for the traffic... was damaged," FDOT spokesman Michael Goldman said. "That means it can't hold the weight, it can't hold the traffic. That's why we had to shut the bridge down for safety reasons."

Channel 4 has learned the ship that struck the bridge about 2 p.m. was the USNS Harry L. Martin, a Sealift Command vessel that was being moved from one part of the North Florida Shipyards to another.

A vertical ramp on the stern of the ship shows damage.

IMAGES: Ship hits Mathews Bridge | UNCUT:Cell phone video  
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The U.S. Coast Guard said the ship was under tow. Crews are enforcing a 200-yard safety zone on both sides of bridge, which is effectively closing a portion of the St. Johns River.

Ship after hitting Mathews Bridge The USNS 1st LT Harry L Martin belongs to Military Sealift Command. It is government owned and managed and operated by civilians, according to the Navy. It is not a commissioned U.S. Navy warship or manned by U.S. sailors, but is a civilian-operated cargo ship owned by the Navy.

Navy officials said the port side stern ramp impacted the Matthews Bridge, and the extent of the damage to the ship is unknown. The ship was empty of cargo when the accident occurred.

There were no reported injuries on the ship or civilian tugboats pulling the ship.

Mathews Bridge Tweets

The height of the vessel from the water line to the top of the portside King Post buttress is 148 feet. The stats on the Mathews Bridge show the height from the bottom of the span to the river is 152 feet. At the time the ship hit, it was empty and the tide was higher than normal.

Capt. Tim McGill, president of the St. Johns Bar Pilot Association, said a number of tug boats were carrying the military supply ship from Blount Island to the shipyards so that Blount Island could be dredged. He said the ship was not under its own power.

McGill said the ship is a commercial vessel which the military charters.

Transportation officials can't say how long it will take to repair the bridge and reopen it to traffic, but they are sure it will not open before next week.

"The damage to the concrete sections of the metal grating is extensive and the bridge will be closed for some time," said Rod Sullivan, a Florida Coastal School of Law professor who specializes in marine incidents.

"Everybody's involved in this," said Jacksonville Sheriff’s Office's Shannon Hartley. "This is affecting our broader community and all the agencies are pitching in to help. Be patient, try to make adjustments whenever possible and just understand that this is going to be a process."

The Captain of the Port lifted the safety zone in the St. Johns River around the Mathews Bridge at 8:15 p.m. Thursday after Florida Department of Transportation bridge inspectors determined there was no threat to river traffic passing below.

Officials said Thursday night the bridge roadway remains closed to all traffic, and the Coast Guard is continuing to investigate the cause of the accident.