HOUSTON -- Up to 2,000 gallons of oil may have spilled into the Gulf of Mexico after a bunker barge struck a bridge in the island city of Galveston, eastern Texas, the US Coast Guard estimated on Thursday.

The source of the leakage from the barge has been contained after the accident, said the US Coast Guard. AP reported that the Coast Guard had deployed a boom, or barrier, to contain the spill.

The Coast Guard said it deployed planes and drones to evaluate the extent of the oil spill on Thursday, while closing about 6.5 miles (10.5 km) along the Gulf Intracoastal Waterway, a busy shipping channel for the region. Galveston is about 50 miles (80.5 km) away from downtown Houston, the largest city of Texas.

"We're pretty confident there was much less oil introduced to the water than we initially estimated," Coast Guard Captain Keith Donohue told a news conference on Thursday.

"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 321-foot barge, which has the capacity to hold 30,000 barrels of oil, was carrying 23,000 barrels, that amounts to nearly 966,000 gallons, when it slammed into a pillar of the Pelican Island Causeway bridge on Wednesday, Rick Freed, vice president of barge operator Martin Marine, told the news conference.

A tugboat lost control of two barges "due to a break in the coupling" connecting them. One of the barges slammed into the bridge, the Coast Guard said.

Freed said an investigation is still underway.

The crash led to the partial collapse of the bridge, forcing the only land connection from Galveston to Pelican Island to shut down. No injuries were reported.

"The harmful consequences of oil are once again impacting our coastal communities, wildlife, and waters," Joseph Gordon with an ocean conservation group named Oceana said in a statement.

The spill will probably have minimal long-term consequences, considering the volume of oil on board the barge, Danny Reible, a Texas Tech University professor, told ABC News on Thursday.

The accident came weeks after a cargo ship slammed into a support column of the Francis Key Bridge in Baltimore on March 26, claiming six lives.