Supermarket pumps in East Anglia were cleared of “faulty” petrol this weekend after a supplier admitted it had traced the silicon contamination which damaged thousands of cars to a series of storage tanks.

Supermarket pumps in East Anglia were cleared of “faulty” petrol this weekend after a supplier admitted it had traced the silicon contamination which damaged thousands of cars to a series of storage tanks.

Harvest Energy, which shares facilities at an oil terminal in Essex with Greenergy, which supplies most supermarket forecourts, said its tests had found “unusually high levels of silicon” in four petrol storage tanks at the site.

The statement came after motorists across the east of England - including several hundred in Norfolk - were forced to shell-out hundreds of pounds to repair a sensor in their car exhaust. Many said they had bought fuel from filling stations at Tesco and Morrisons supermarkets.

Morrisons withdrew unleaded petrol from sale at 41 of its filling stations on Friday, including its Norwich store in Albion Way, which was supplied by the Essex depot. Superstore Tesco also emptied unleaded fuel tanks at forecourts across the region after tests showed they had been contaminated.

On Sunday Tesco and Asda were working to replace unleaded at each forecourts. The supermarkets are promising to pay compensation to customers whose cars have suffered damage.

In a statement Harvest Energy said the contamination had not been detected prior to sale because routine standards testing of petrol did not include a test for silicon as it would not normally be in the fuel.

“We will now be testing for silicon as a matter of course,” the company said.

Harvest Energy said it had isolated the higher silicon fuel, and could guarantee no further contaminated petrol would be distributed. The firm is working to discover the source of the contamination, which may have occurred at the terminal or from contaminated fuel

brought into the site from elsewhere.

The company also said it had appointed an independent inspection company to test fuel stocks at more than 100 petrol stations across the South East over the weekend.

Harvest Energy's managing director Franco Bussandri said: “We are very sympathetic to the plight of motorists who have been affected by this problem with unleaded petrol.”

Tesco is in the process of emptying unleaded petrol tanks in around 150 forecourts in the South East, and refilling them with fuel which had been tested and found uncontaminated with silicon.

Morrisons said it was still testing the fuel to see if it was contaminated, but assured consumers they would not be left out of pocket if a product sold to them had not been fit for purpose.

Asda said it was replacing unleaded petrol at the 30 forecourts in the South East which are supplied from the affected depot as a “precautionary measure”.

Tests had shown only very low levels of silicon in Asda's fuel, but the supermarket giant said it would be running down the unleaded tanks at the sites and refilling them with new petrol over the weekend.