Early estimates indicate a barge collision in Galveston, Texas, may have spilled up to 2,000 gallons of oil in surrounding waters, the U.S. Coast Guard said Thursday.

The barge had drifted away from the tugboat pulling it and 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.

State officials said early cleanup efforts have not identified any impacted wildlife.

Video shows splotches of oil that spilled from the barge into Galveston Bay after the crash.

"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 U.S. Coast Guard said it has deployed a boom, or barrier, to contain the source of the spill and was using drones and personnel to determine how much oil was in the water.

The spill led to the closure of about 6.5 miles of the waterway.

The Coast Guard said Thursday the tugboat lost control of the 321-foot barge "due to a break in the coupling" that had connected the two vessels.

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 are unaffected.

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.