A British consumer safety watchdog is warning shoppers that using counterfeit chargers and adapters for electronic gadgets could place them in grave danger, after basic tests showed that almost all of them could not meet safety standards.

Out of 400 counterfeit Apple aapl chargers tested by Trading Standards, only three had sufficient insulation to withstand high voltage, according to the BBC — that translates to a failure rate of 99.25%.

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The BBC reports that the watchdog had obtained these counterfeits from eight countries, including Australia, China and the U.S.

“It might cost a few pounds more, but counterfeit and second-hand goods are an unknown entity,” said Leon Livermore, the chief executive of the U.K.’s Chartered Trading Standards Institutes, urging consumers to stick with genuine electrical goods from trustworthy sources.

He warned that fakes “could cost you your home or even your life, or the life of a loved-one,” according to the BBC.

Apple filed a lawsuit in October against a U.S. vendor that had sold counterfeit chargers on Amazon’s e-commerce platform, claiming them to be genuine.

It also alleged that nearly 90% of all purported Apple adapters and chargers sold on Amazon amzn were counterfeit.

For more on Amazon, watch Fortune’s video.

Amazon has since ramped up its efforts to eradicate merchants selling fake goods on its marketplace. In mid-2013, the Cupertino, Calif.-based tech giant launched a global program offering to take back unauthorized or counterfeit adapters and replace them with Apple-manufactured ones at a reduced price.