London, March 1 (Reuters): Petrol firms carried out checks today into reports that a rogue batch of fuel was damaging hundreds of car engines but said that so far they had found no evidence of contamination.

Trading standards officials are investigating up to 100 complaints from motorists in southeast England. Television stations said they had been bombarded with emails from angry drivers saying their vehicles had broken down or were running roughly after leaving filling station forecourts.

The Society of Motor Manufacturers and Traders (SMMT) said it believed suspect fuel might have damaged sensors in some cars’ systems, leading them to cut power to prevent damage to the engine.

“It’s still fairly unclear what’s going on,” said SMMT spokesman Nigel Wonnacott.

“It’s affecting all types of cars but it tends to be cars which are 3 years old-plus. It doesn’t seem to be so much of a problem ... with brand new cars,” he added. Ian Hillier of the Trading Standards Institute said the problem only seemed to be hitting cars using unleaded petrol.

“Officers are investigating these complaints, and samples of fuel from some of the affected cars are being tested for contamination, as are the contents of the pumps from which the petrol was drawn,” he said.

Results of the tests are due by the end of the week.

SUPERMARKET FUEL?

Several motorists blamed petrol they had bought from supermarkets Tesco and Morrisons.

Both companies said they had carried out tests and found no evidence of contamination.

”Whilst we cannot currently trace any problem back to Tesco fuel, we will of course continue to urgently work with our supplier to identify what might be behind it,” a spokesman said.

Morrisons said it had tested every batch of unleaded petrol to ensure it met British and European standards. It too had found no contamination.

Wal-Mart's Asda, which had received about 80 complaints, said the problem appeared to have arisen from a depot east of London which supplied about 30 of its forecourts.

”We are investigating and if there is a consumer issue we will deal with it,” Asda Chief Executive Andy Bond said on the margins of a retail summit in London.

Clifford Jones, an engineering academic at the University of Aberdeen, said there were three plausible explanations:

A refinery might have allowed other products to mix with the gasoline; an octane enhancer might not have been added to gasoline which needed one, or a biofuel like bioethanol might have been put into cars which were not designed to run on them.

”We have no reports of quality issues with petrol supplied from UK refineries,” said the UK Petroleum Industry Association (UKPIA), which represents Britain's nine main refining firms.

It added the source of the problem might be a batch of fuel supplied to“some large independent retail sites”.

Most of the fuel sold by supermarkets in the southeast comes from the Vopak terminal in the Thames Estuary, through independent oil supplier Greenergy.

Greenergy, which supplies both Morrisons and Tesco, said it had found no abnormalities.

”We have no reason to believe it is bioethanol but to rule it out is premature,” a company spokeswoman said.

(additional reporting by Nigel Hunt and Rachel Sanderson)