Hundreds of tonnes of oil estimated to still be inside an offshore pipeline that has been leaking for a week

Hundreds of tonnes of oil could still be inside an offshore pipeline that has been leaking for a week. The estimate was revealed as Shell continues to try to stem the flow on the seabed near the Gannet Alpha platform, about 112 miles east of Aberdeen.

Since the leak started last Wednesday, more than 200 tonnes of oil has spilled into the North Sea, making it the worst single leak in the region for more than a decade.

The initial large leak was stopped the following day, but it later emerged that a smaller flow from the same source had been detected. That leak was described as being in an "awkward" place surrounded by marine growth.

Shell technical director, Glen Cayley, said the company's pipeline maintenance programme had let it down, according to a report in the Press and Journal newspaper. "We are talking about hundreds of tonnes of additional oil in the pipeline that we need to preserve and keep there," Cayley told the paper.

"Until we have completely eliminated the leak and secured this pipeline, I would say there is still risk." He added that work is continuing to figure out how to fix the breach.

Environmental groups have strongly criticised Shell for its handling of the spill, complaining about a lack of timely information.

(AP / Guardian.co.uk, 17/08/2011)