GALVESTON, Texas (AP) — Early estimates indicate up to 2,000 gallons of oil may have spilled into surrounding waters when a barge carrying fuel broke free from a tugboat and slammed into a bridge near Galveston, Texas, the U.S. Coast Guard said Thursday.

The barge crashed into a pillar supporting the Pelican Island Causeway span on Wednesday. The impact caused the bridge to partially collapse and cut off the only road connecting Galveston to Pelican Island, the Coast Guard said.

Video shows splotches of oil had spilled from the barge into Galveston Bay. Jeff Davis of the Texas General Land Office said during a news conference Thursday that early cleanup efforts have not identified any impacted wildlife.

The barge has the capacity to hold 30,000 barrels, but was holding 23,000 barrels — approximately 966,000 gallons — when it struck the bridge, Rick Freed, the vice president of barge operator Martin Marine, said at the news conference. Freed said the only tank that was compromised in the crash was holding approximately 160,000 gallons, which is the “complete risk.”

“We’re pretty confident there was much less oil introduced to the water than we initially estimated,” Coast Guard Capt. Keith Donohue said.

“We’ve recovered over 605 gallons of oily water mixture from the environment, as well as an additional 5,640 gallons of oil product from the top of the barge that did not go into the water,” Donohue said.

The Coast Guard said earlier that it had deployed a boom, or barrier, to contain the spill, which forced the closure of about 6.5 miles (10.5 kilometers) of the waterway.

A tugboat lost control of the 321-foot barge “due to a break in the coupling” that had connected the two vessels, the Coast Guard said.

“Weather was not a factor, at all, during the coupling issue,” Freed said. When pressed for more details on how the two vessels became disconnected, he said: “It’s under investigation right now, and I really can’t disclose anything further until the investigation is through.”

On Thursday, the barge remained beside the bridge, weighed in place by debris including rail lines that fell onto it after the crash.

The bridge, which provides the only road access between Galveston and Pelican Island, remained closed to incoming traffic, but vehicles leaving Pelican Island and pedestrians in both directions were able to cross.

Texas A&M University at Galveston, which has a campus on Pelican Island, urged staff and faculty to leave and said it was closing the campus, although essential personnel would remain.

“Given the rapidly changing conditions and uncertainty regarding the outage of the Pelican Island Bridge, the Galveston Campus administration will be relocating all Texas A&M Pelican Island residents," through at least Sunday, it said in a statement late Wednesday.

Fewer than 200 people related to the school were on the island when the barge hit the bridge. Spokesperson Shantelle Patterson-Swanson said the university would provide transportation and cover the housing costs of those who choose to leave, but underlined that the school has not issued a mandatory evacuation.

Aside from the environmental impact of the oil spill, the region is unlikely to see large economic disruption as a result of the accident, said Maria Burns, a maritime transportation expert at the University of Houston.

The affected area is miles from the Gulf Intracoastal Waterway, which sees frequent barge traffic, and the Houston Ship Channel, a large shipping channel for ocean-going vessels.

The accident came weeks after a cargo ship crashed into a support column of the Francis Key Bridge in Baltimore on March 26, killing six construction workers.

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Gonzalez reported from McAllen, Texas.

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This story corrects the spelling of the name of a University of Houston's maritime transportation expert. Her name is Maria Burns, not Marcia.