Workers are being taken off a North Sea platform amid ongoing problems with diesel entering its water supply.
Staff on BP’s Magnus installation were warned of the issue earlier this month but an investigation has failed to find the source of the contamination.
The problem was first discovered when workers reported a smell of diesel when showering.
BP said 40 non-essential staff were being taken off the platform but said the level of contamination was low.
Earlier this month, workers were told to drink only bottled water while an investigation was carried out.
Narrowly failed test BP said it had flushed the tanks and was confident there was no longer any contamination.
But it has now said the supply narrowly failed a quality test last week.
The company said the investigation into the root cause of the problem was ongoing and workers of non-essential staff were being moved to lessen the impact.
About 140 people will remain on the platform, which is about 100 miles (161km) north-east of Shetland BP said the level of contamination to the water supply was far below the level that could cause health problems.