Expecting father killed in fiery explosion while on 4WD adventure with mates

A 23-year-old expecting father has died after a horror accident while on a four-wheel-drive adventure with mates.

Jack Aubrey Kinneen approached a fire near a bush track in the early hours of September 22 in Pinjar, in Perth's north.

An explosion occurred as he approached the blaze, and despite the efforts of the six friends he was with and paramedics, Kinneen died at the scene.

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He left behind a pregnant partner, their baby boy due in weeks.

"He was the most charismatic, funny, friendly and loving boy," his sister wrote.

"Jack's friends said he was 'happy and laughing' when it happened.

"Rest in peace Jacky Boy, forever in my heart

Police said on Tuesday the fire appeared to have been deliberately lit and that its "structural components" caused the explosion that killed Kinneen.

Detectives from the state's homicide squad are now seeking more information about the blaze, including wanting to talk to two people who were seen near the incident.

"Detectives would like to speak to two people who were seen in the area at the time," police said in a statement.

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"The first person is a male, about 40 years old with balding hair.

"The second person is a female who was driving a silver or bronze Holden Commodore sedan – believed to be an early 2000s model."

Detectives won't reveal exactly what exploded. The blaze was known to be a small isolated fire but why it was loose in the early hours of the morning is unclear.

Detective Sergeant Jeremy Spivey said there was nothing to indicate the fire was lit with the intention of harming anyone.

Anyone with information about the fire or footage of the incident has been asked to contact police.