SAN LEON, TEXAS -- Coast Guard officials said a barge that collided with a tanker in the Houston Ship Channel may have spilled 700,000 gallons, or nearly all of its cargo, into Galveston Bay.

The Coast Guard had said earlier that 500,000 gallons of oil spewed into the bay after the accident. But officials considered adjusting that estimate after salvage crews found nothing in a once-submerged cargo tank they expected to contain about 200,000 gallons of oil.

"It looks like a lot of the oil may have escaped from it," Coast Guard Capt. Thomas Greene said. He said officials were rechecking ship manifests to determine exactly how much oil was aboard the vessel.

The state health department, meanwhile, announced that a ban on fishing in the bay, begun Thursday, would be partially lifted today in several areas apparently unaffected by the oil.

The accident occurred a week ago when the Greek tanker Shinoussa collided with two barges in the Houston Ship Channel, nearly sinking one barge.

Limited ship traffic was allowed in the Houston channel, closed since Saturday, as an investigative hearing into the accident resumed in Houston. The second mate of the tanker testified its pilot was "racing" before the accident, and then tried to cover up how fast the ship was traveling.