ST. JOHN'S, N.L. -- It's not possible to clean up what remains of an estimated 12,000 litres of oil spilled from the Hibernia platform off Newfoundland last month, according to the board that regulates the industry.

The Canada-Newfoundland and Labrador Offshore Petroleum Board said in a statement Thursday that surveillance by satellite, air and sea in recent days showed the oil had become so diluted that it can no longer be recovered or dispersed.

Production at the Hibernia platform, located about 315 kilometres east of St. John's, has been shut down since the July 17 spill.

Last Thursday, the board estimated the remaining volume of oil kin the water at 1,070 litres.

This week the Hibernia Management and Development Company reported three of the six oiled seabirds recovered from the area had died.

The company has said the spill happened during routine activities. The petroleum board said it is continuing to monitor wildlife and is investigating the incident.

The latest spill follows the largest in the history of the province's offshore industry, when about 250,000 litres of oil flowed into the ocean from Husky's SeaRose platform last November.