A clean-up operation has begun after a barge carrying nearly 1 million gallons of oil collided with a ship off the coast of Texas on Saturday afternoon.

The clean-up has prevented about 60 ships, including three cruise ships, from sailing in or out of Galveston Bay, a popular bird sanctuary in the Gulf of Mexico – where the Deepwater Horizon oil well, owned by BP, spilled millions of gallons of oil in 2010.

Coast Guard Petty Officer Andy Kendrick said it is not known how much marine fuel oil, also known as special bunker, has spilled.

At least one of the vessel's tanks - which each carry up to 168,000 gallons of oil – sprang a leak following the collision, and a large slick was visible on the surface.

The barge, owned by Kirby Inland Marine, was being towed from Texas City to Bolivar when it collided with the 585ft-long ship Summer Wind.

Kendrick said skimmers are trying to recover the oil and a boom is in place to protect the area's environmentally sensitive mud flats. The remaining oil is being removed from the sunken barge.

Jim Suydam, a spokesman for the General Land Office, said the oil is "sticky, gooey, thick, tarry stuff. That stuff is terrible to have to clean up," he said.

Conservationists fear for tens of thousands of wintering birds in the area.

Richard Gibbons, conservation director of the Houston Audubon Society, said: "The timing really couldn't be much worse since we're approaching the peak shorebird migration season." However, Kendrick said there have been no reports of wildlife being affected.

This week marks the 25th anniversary of the Exxon Valdez oil spill in Alaska in 1989, which spilled 260,000 gallons of oil into the Port of Valdez in one of the world's worst environmental disasters.