Updated

The worst Texas oil spill in more than 15 years was contained Monday, and authorities credit a massive emergency response with averting an environmental disaster.

About 462,000 gallons of oil spilled when an 800-foot tanker headed for an Exxon Mobil Corp. refinery in Beaumont collided Saturday with a vessel pushing two barges. As of Monday, roughly 220,000 gallons of oil had evaporated or dispersed, the U.S. Coast Guard said.

No injuries have been reported, but Port Arthur residents were evacuated after the spill while officials tested the air quality. So far only two oil-covered birds have been reported; one of them was captured and cleaned up, and the other flew away.

More than 60 vessels and 550 people from the Coast Guard, the state, the shipping company and others responded to the spill. More than 11 miles worth of the plastic walls known as booms are floating around the spill, and 27 skimmer boats were removing the oil floating on the water.

"This response has helped contain this oil and keep it from becoming a catastrophe," said Texas General Land Office spokesman Jim Suydam. "Had this oil escaped the ship channel, it could have been a catastrophe."

It was the largest spill in Texas since 1990, when a Norwegian tanker spilled 4.3 million gallons about 60 miles off Galveston.

Two sensitive wildlife areas near the weekend spill remain unaffected by it. The spill is mostly contained in a 2-mile stretch of the Sabine Neches Waterway near Port Arthur, about 90 miles east of Houston. The estuaries and other delicate environments are crucial for fish, shrimp and "everything that lives in the Gulf," Suydam said.

Environmental watchdogs were encouraged by the speedy response but concerned about what air pollutants the people nearby were exposed to.

Hilton Kelley, a Port Arthur environmental activist and head of the group Community In-Power and Development Association, said he was near the water Saturday during the evacuation. He said the smell was so overpowering that he had to put on a respirator mask, and that he told two women walking down the street with their coats over their faces to leave because it was dangerous.

"The fumes were just unbearable," he said. "Our main concern is the number of people who might have been impacted over the long term by the fumes."

The evacuation was lifted Saturday night. The Texas Commission on Environmental Quality was monitoring the air and water quality and said there were no reports of problems with drinking water or wastewater.

"We've learned a lot over the years how to do this right," said Tom "Smitty" Smith of the activist group Public Citizen. "The downsides, of course, are the long-term impacts of the people who are exposed to the emissions."

The shipping channel was closed Monday, and it remains unclear when it will reopen, the Coast Guard said. Coast Guard Petty Officer Larry Chambers said there are currently 13 vessels waiting offshore to get into the waterway and 11 waiting to get out. He said about a dozen tankers move through the waterway each day.

AET Tankers, the company that owns the vessel called the Eagle Otome, said it's still unclear exactly how the accident happened that left a 15-foot-by-8-foot hole in the tanker. The National Transportation Safety Board and the Coast Guard are investigating. The Coast Guard is reviewing radio transmissions from the vessels as part of the investigation but is not releasing any information from them yet, Chambers said.

A spokesman for AET Tankers, a Malaysian company with offices in Houston, said the company is cooperating with the investigation and working with the Coast Guard on the cleanup.

"It was our product that spilled and right now, we are the ones responsible for cleaning it up," spokesman Darrell Wilson said.