Never-before-seen footage of Michael Jackson’s hair catching fire while he filmed an ad in 1984 - the accident said to have led to his addiction to painkillers and plastic surgery - has been released by a US magazine.

Jackson and his brothers were filming a Pepsi commercial at the Los Angeles Shrine auditorium in front of a crowd of 3,000 adoring fans when fireworks exploded too early on the sixth take.

The dramatic images show flames leaping from Jackson's head as, apparently unaware of what has happened, he continues his dance routine. It is several seconds before his brothers, his band, roadies and film crew leap to his aid, beating out the flames.

Jackson can then be seen with his face contorted in pain, clutching at his scalp where a bald spot has already appeared. Aides take him by the arms and hustle him away to hospital.

“He was never the same after the accident,” writes the magazine Us Weekly, which released the footage on its website.

“To relieve the second and third-degree burns on his scalp and body (and later to help him tolerate multiple surgeries on the scorched spot on his head), Jackson was prescribed several medications - which kicked off his addiction to painkillers and obsession with plastic surgery.”

The “King of Pop” died on June 25 at the age of 50 after suffering a heart attack. A US coroner has said that toxicology reports from Jackson's body should be ready within a week.

Los Angeles police said last night that they were investigating Jackson’s death, but would not confirm it was being treated as a homicide investigation, as reported by TMZ.com, a gossip website.

TMZ said it had been told by several sources in the justice system that the evidence pointed to the painkiller Propofol (Diprivan) as the main cause of Jackson’s death.

Pictures have emerged purporting to show needle puncture marks on the star’s ankles and a large wound on his right shin, thought to have been caused by his injection of drugs.

Last night Tito Jackson, the star's brother, waded into the debate on Jackson's legacy by insisting that the star was the biological father of all three of his three children.

Tito said the children all bore a family resemblance, with Blanket - whose real name is Prince Michael II - having the same eyes as the singer. Blanket was born to a mystery surrogate mother that the singer is reported never to have met.

“Them eyes are Michael over again. I see a lot of Michael in him,” Tito, 55, told the Daily Mirror.

He also dismissed suggestions that the children were too pale to be Jackson’s. “Just because they look white doesn’t mean they are not his. Prince looks just like my grandfather.

"There’s no question they are Michael’s. They are 100 per cent his...They remind me of me and my brothers when we were growing up.”

Despite growing up in the media spotlight, the children were all “very, very normal”, Tito added. He said they enjoyed wearing masks when they went out and that they knew that they and their father were famous.

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