Image copyright William Brown/Facebook Image caption William Brown died after a vape pen exploded while he attempted to use it

An exploding vaporiser pen resulted in the death of a 24-year-old Texas man, a post-mortem examination has ruled.

The pen's battery blew up when William Brown tried to use it, sending shards of metal into his face and neck and severing an artery.

He died two days later in hospital of a stroke, in what is at least the second such death in the US.

Malfunctioning e-cigarette batteries have caused hundreds to thousands of similar injuries, US reports say.

The Tarrant County Medical Examiner's Office found on Tuesday that shrapnel from the vape pen's exploding battery impacted Mr Brown's skull, severed his carotid artery and ultimately caused his death on 29 January.

The incident took place in the parking lot of a vape shop in Fort Worth, Texas on 27 January.

Mr Brown had visited the shop to seek help using a Mechanical Mod style pen - a model known to have issues, a local CBS News affiliate reported.

He attempted to use the pen in the car when the battery exploded with enough force to melt plastic in the vehicle and fling metal debris into Mr Brown's face.

The owners of the shop called an ambulance after seeing Mr Brown bleeding in the parking lot.

"When they x-rayed him, they found the stem, the metal embedded to where the blood flows up to the brain," Mr Brown's grandmother, Alice Brown, told WFAA News.

Doctors were apparently unable to remove the metal surgically. Mr Brown was placed in an induced coma, but eventually passed away.

Mrs Brown, who raised Mr Brown, told the Star Telegram her grandson was just weeks away from his 25th birthday.

"It just hurts so bad. Now he'll never see that birthday. It's a waste of the things he could have accomplished."

The 24-year-old was a licensed electrician and not a regular smoker - he had been testing out the pen for the first time, his grandmother said.

She hopes his death gives others pause before trying an e-cigarette.

"If anything, I hope it stops someone," she said. "I don't know how many more people will have to die."

Image copyright Reuters Image caption The US Food and Drug administration says e-cigarette use by young Americans has been on the rise

How common is this?

Last May, a 38-year-old Florida man was also killed by an exploding vape pen. Tallmadge D'Elia was burned on 80% of his body and died when metal pieces entered his skull.

A US government report says there have been 195 documented cases of exploding e-cigarettes between 2009 and 2016.

The National Fire Data Center found 29% of exploding vape pen incidents from January 2009 to December 2016 had caused severe injuries.

Another report from the University of North Texas Health Science Center looked at US emergency room data from 2015 to 2017 and found 2,035 e-cigarette related explosion and burn injuries - far more than previous reports.

The researchers said regulation and surveillance of e-cigarette devices "is urgently needed".