Environmental health officer Hittess Vaghela became aware of a problem when the contaminated product was imported from Zimbabwe.

A small quantity of a batch that arrived at Gatwick Airport was found in a shop in High Town and destroyed.

But eagle-eyed Hittess spotted more jars of Willards smooth peanut butter on sale in Zambezi Foods in High Town Road and launched an investigation.

The 29-year-old, who joined the council's environmental and consumer services department in May 2003, sparked Luton's first ever national food hazard warning.

He discovered that two out of three of the batches sampled failed food standard tests and were found to contain high levels of aflatoxin, which causes cancer in animals and is poisonous to humans.

Hittess, who has two masters degrees and a science degree from his university years, said there were more than 100 jars both in the shop and its nearby warehouse.

He added: "The retailer not only sells direct to the public but is also a distributor to other shops across the country.

"They quickly agreed to stop selling the affected batches and put up a notice asking customers to return contaminated products for a full refund.

"They also alerted businesses that had received supplies and arranged for them to issue a warning to their customers. I am glad Zambezi Foods took this matter seriously and fully co-operated with the council."

Zambezi Foods owner Marvin Muchando said: "This is the first time we have had a problem since the business started four years ago.

"We began importing this peanut butter a few months ago and one batch was recently found to be contaminated during a routine check.

"High toxin levels were found, although they were not particularly harmful to humans. We immediately withdrew the jars and put out a notice.

"There were only a few cases containing a total of 120 jars in this batch and just a few had been distributed to shops in the London area and one shop in High Town."