Image copyright Facebook Image caption Two pieces of the vape pen were in Tallmadge D'Elia's cranium

A US man died when a vape pen blew up and projected fragments into his skull, a post-mortem examination has found.

Tallmadge D'Elia also suffered burns over 80% of his body in a fire on 5 May caused by the exploding e-cigarette, according to forensic officials.

The 38-year-old's body was discovered by firefighters in the burning bedroom of his family home in the beach resort of St Petersburg, Florida.

It is believed to be the first US death from a vape pen explosion.

The television producer's death has been ruled an accident.

The Pinellas-Pasco Medical Examiner said the official cause of death was "projectile wound of head", reports the Tampa Bay Times.

Two pieces of the vape pen were found in his cranium, according to the autopsy.

Media playback is unsupported on your device Media caption Could vaping help smokers stub out cigarettes for good?

The report said emergency crews encountered "extensive" fire damage to the bedroom where the body was found, but minimal smoke.

The electronic cigarette was manufactured by Smok-E Mountain, said the medical examiner.

Christopher D'Elia, the dead man's father, told ABC Action News it was a "terrible shock".

"Anybody who has lost a son doesn't want anybody else to lose a child to something like this," he said.

How did the device explode?

It's not entirely clear and is not written in the post-mortem examination report.

The vape pen that Mr D'Elia was using was a so-called mechanical mod, meaning it drew power directly from the battery and did not regulate the voltage in the same way as other e-cigarettes.

The president of the American Vaping Association told the New York Times that most other e-cigarettes have more safety features than mechanical mods. Such safety features can include computer chips.

A representative of the manufacturer, Smok-E Mountain, blamed the device's battery for the explosion when speaking to ABC Action News. They also said it might have been down to the mouthpiece.

Vape pens use lithium-ion batteries, favoured in smartphones and other portable electronic devices because they can provide high amounts of electricity using little space.

They are used throughout the world with few incidents, but in 2016 Samsung halted sales of the Galaxy Note 7 phone because some were catching fire when the batteries short-circuited.

Are vape pens safe?

According to the US Fire Administration, between 2009-16 there were 195 separate incidents of explosions and fires involving an e-cigarette, resulting in 133 acute injuries, 38 of them severe.

In 2015, an e-cigarette exploded in the face of a 29-year-old Colorado man, breaking his neck and shattering his teeth.

A fire in January this year at Denver International Airport was blamed on a vape pen's lithium-ion battery.

For safety, the Food and Drug Administration (FDA) in the US recommends: