LONDON—Investigations were under way on Thursday into complaints from motorists who believe their cars had suffered problems resulting from contaminated petrol.
Retailers and suppliers said they were carrying out tests on fuel but had so far found no evidence of any abnormalities.
Trading standards authorities said they were looking into complaints from up to 100 motorists in southeast England where the problem is centred.
"Officers are investigating these complaints and samples of fuel from some of the affected cars are currently being tested for contamination, as are the contents of the pumps from which the petrol was drawn," said Ian Hillier of the Trading Standards Institute.
He said an analysis of the samples was due by the end of the week.
"The problem appears to be restricted to unleaded petrol and motorists experiencing problems with their cars should take them to a garage," he added.
The BBC reported it had been contacted by more than a thousand motorists whose vehicles had suffered engine problems such as shuddering and stalling.
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.
"Our advice is that motorists should keep all fuel receipts and note the mileage for each purchase," it said.
"If your car does seem to be affected, you should contact your car dealer and if necessary the car maker's customer service departments for advice."
The SMMT said the sudden rush for replacement sensors meant all available ones had gone and car makers were "working flat out" to get replacements to dealers.
The UK Petroleum Industry Association (UKPIA), which represents the nine main refining companies in Britain, said the problem did not seem to be widespread but was limited to London, east and southeast England.
"We have no reports of quality issues with petrol supplied from UK refineries," UKPIA said, adding that the source of the problem might be a batch of fuel supplied to "some large independent retail sites".
Supermarket chain Tesco, Britain's biggest retailer, said it was investigating reports that drivers had experienced problems after filling up at its forecourts.
"We are aware that customers of other supermarkets have also reported difficulties," a Tesco spokesman said.
"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."
Independent oil firm Greenergy said it was examining whether the problem was related to its supplies.
"So far we have conducted extensive tests on the fuel supplied to Tesco and Morrisons," it said in a statement.
"We have found it is fully compliant with BSEN 228—the independent standard everyone works to."
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