More than 150,000 gallons of diesel oil has escaped from the Ecuadorean tanker washed up on one of the Galapagos Islands.
A pounding surf has caused new splits in the ship's hull, which was carrying about 243,000 gallons of fuel.
It ran aground last Tuesday in a bay on San Cristobal Island, populated by rare marine species.
Ecuador's environmental minister, Rodolfo Rendon says the spill has spread about 186 square miles.
The boat tilted heavily to its starboard side some 550 yards offshore on Friday when the leak began.
A team of US experts, including 10 members of the US Coastguard's pollution response National Strike Force, is helping to remove the remaining fuel from the ship's storage tanks.
President Gustavo Noboa has demanded a "detailed report" about the cause of the accident, which officials blame on navigational error.
Police on San Cristobal say no charges have been filed against the ship's captain, Tarquino Arevalo, who remains on the island, or against his company, Acotramar.