Two cars on opposite sides of the Whanganui River destroyed by fire within an hour

What remains of Rebecca Wilson's Honda Fit. Jacob McSweeny.

The police are looking into what caused two car fires in Whanganui overnight.

The fire service said it became aware of one car ablaze on Roberts Ave in Aramoho at midnight before it was told of another on Number 3 Line in Whanganui East just moments later.

Both cars were engulfed in flames when fire trucks arrived but they were able to put the fire out before it reached the petrol tank.

The owner of the car in Aramoho, Rebecca Wilson, said she couldn't believe it when her husband told her the car was on fire.

"It wasn't like smouldering or anything like that, it was just fully engulfed.

"It was bloody terrifying. I was waiting for it to explode and you know, kill us all. It was horrible. One of the scariest things I've ever seen."

She said some parts of the car like the tyres did explode. "It was the flames, they were just scary ... but the gas tank didn't explode."

Wilson, who moved to Whanganui from Whangarei two years ago said it was probably the work of an arsonist.

The second car destroyed in the night by fire. This one was on Number 3 Line in Wanganui East.

"The cops seemed to think someone did it and the fire brigade did too because apparently cars don't just catch on fire.

"It happened in Number 3 Line as well. When the fire brigade was just finishing up here, we were just chatting [and] they got another call.

"I think it's random. We've only been here a couple of years ... we haven't done anything to piss anyone off that I know of."

She had owned the car for about a year.

"I liked it. It's amazing how much it melts.

"I usually park it in the carport but I was cleaning out the garage over the weekend and I just needed more room. I don't usually park it out there at all. I like having it behind our gate where I think it's safe."

She said she had insurance.