A poor quality USB charger is being blamed for the death of a woman who was electrocuted in New South Wales earlier this year.

The 28-year-old woman was found dead at a home in North Gosford, on the state's central coast, on April 23.

She was electrocuted while using a USB charger as she was listening to audio through earphones.

"We know absolutely that the charger itself failed, and that it arced between the 240 volt input and the five volt output. So that's definitive," said NSW Fair Trading's Lynelle Collins.

"We've got photos, we've got proof that's been dismantled, so we know that the charger failed. But the coroner is still investigating the root cause."

The Department of Fair Trading investigated and found the charger she was using was not compliant with Australian standards.

The trader who sold the charger in Campsie, in Sydney's south-west, is being questioned by police and may face possible charges.

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Fair Trading Commissioner Rod Stowe has warned people about the danger of using non-approved products.

"Fair Trading has detected a large number of these [chargers], along with travel adaptors and other power boards, at a store in Campsie and these have been removed from sale," he said.

"My younger son was using a phone recharger in our car without us knowing it wasn't an approved item, and it managed to blow the fuses in the car. So that was a quick indication to me that there was a problem.

The NSW Department of Fair Trading warn non-compliant devices pose a serious risk of electrocution or fire. ( NSW Department of Fair Trading )

"These devices pose a serious risk of electrocution or fire.

"We will continue to ensure that we undertake inspections around New South Wales."

The department is warning consumers against using any devices while they are plugged in and charging.

The unapproved devices are often made of inferior plastics and other insulation materials. The chargers found by Fair Trading had no insulation on pins, or approval marks.

"These are made at a very cheap price. Within Australia, the pins that get plugged into a power point need to be insulated. The construction needs to be sturdy, and has approval marks on the actual products themselves," Ms Collins said.

"It's a unique number, the approval number, and it's an 'N' for NSW, if it's been approved within NSW, and a triangle with a tick. Sometimes that's quite small, and difficult to read, but as long as the marks are there, it's acceptable."

Mr Stowe has defended the two month delay in releasing the information about the case.

"We moved as quickly as we can. I understand initially there wasn't clear information about the cause of the fatality," he said.

The department recommend that anyone in possession of unapproved devices bend the pins on the chargers and dispose of them immediately.