Householders with Beko frost-free fridge freezers are being urged by fire experts to check that the model they own is not one at the centre of a product safety warning, just days after a serious tower block blaze which has now been confirmed to have been caused by one of the manufacturer's faulty appliances.

The London Fire Brigade (LFB) believes the incident in Bermondsey, south London underlines the potentially serious danger of failure in the appliances which has already been flagged up by the company as a cause for concern. It is believed there could be as many as 500,000 of the potentially faulty fridge freezers still in homes and businesses throughout the UK.

In the Bermondsey blaze last Tuesday one woman was treated for smoke inhalation and another 40 forced to flee the tower block. Investigators had thought initially that the fire was caused by lightning during a thunderstorm, but have now confirmed that it was caused by a faulty Beko fridge freezer.

Fire chiefs are urging people to check if they own the particular models of Beko fridge freezer, which were manufactured between January 2000 and October 2006. There are believed to have been 20 fires in the capital involving the fridge freezers since 2008, which left 15 people injured and one dead. The coroner's report on the latter is outstanding.

People who own any of the appliances should contact Beko via their website – www.beko.co.uk – or calling their free phone number on 0800 009 4837 between 8.00am and 6.00pm Monday to Friday.

Over the past three years LFB's fire investigation team has been working to establish the link between a faulty defroster timer switch on the appliances and a number of house fires attended by its firefighters. The problem occurs when water gets into the defrost timer switch in the fridge freezer, which can lead to an electrical malfunction resulting in plastic components and other highly flammable insulation inside the appliance catching fire.

The brigade formally alerted Beko to the problem in June 2010 and following meetings between Beko and fire investigators, the manufacturer has been trying to locate the products so that the fault can be corrected. However, LFB believes more needs to be done to alert people to the potential danger.

Beko said in a statement that it was co-operating fully and that it would carry out free modifications to any of the faulty models: "We have contacted all retailers who sold these products to seek their help in identifying affected customers from their sales records. This has allowed us to mail these customers to make them aware of the issue and to urge them to contact our freephone number to arrange the modification.

"We are working with a major electronics retailer to contact owners of these products and carry out a free of charge modification to replace the defrost timer. We have adopted a phased approach which allows us to make maximum use of their resource."

Beko said it had contacted over 200,000 owners and modified 11,000 fridge freezers to date.

But LFB's assistant commissioner for fire safety regulation, Steve Turek, said: "Any fire can be lethal but we are particularly concerned about this because fires involving any sort of fridge freezer develop rapidly and produce an enormous amount of toxic smoke.

"Our expert fire investigators have had to work for a long time to confidently establish these faulty fridge freezers as the cause of a number of serious fires. Having established this link, we have worked closely with Beko to ensure the public is kept safe.

"However, we urge everyone who has a Beko fridge freezer to check it is not one of those highlighted by the company as potentially faulty. We would also urge everyone to make sure they have a working smoke alarm in their house."