Brodie Kostecki has backed up his maiden Supercars win with a second triumph in as many days after being cleared following a post-race investigation.

The Erebus driver took the chequered flag in a wild 13-lap sprint around the Australian Grand Prix circuit on Saturday.

However, Kostecki was subject to an investigation as stewards looked into an "unsafe release".

But no action will be taken against the 25-year-old, who was confirmed as a two-time race winner, finishing ahead of defending champion Shane van Gisbergen.

Kostecki's Coca-Cola Racing teammate Will Brown came in third after Bryce Fullwood and Will Davison were given 15-second penalties.

Davison and Fullwood crossed the line second and third, but were classified 11th and 12th after their time penalties were applied.

Kostecki started from pole and was able to survive some serious carnage in the field.

He was unaware he was under investigation when speaking after the race.

"It was a good start, just got a clean jump off the line," Kostecki said

"I made a pretty bonehead move and she was still quick even though I was missing half the front there.

"It's great to reward the team with finishes like this ... I made a pretty stupid error and almost cost me the race."

In another dramatic race, a car caught on fire for the second time in as many days.

Ford veteran James Courtney's Mustang was engulfed in flames, with the vision even more dramatic than when Nick Percat's car went up on Friday.

"I saw the flames and I said to the guys, 'I could smell something from the left-left corner'," Courtney said.

"I could smell it and I tried to get to the pits. Just all the fire stuff to try and save the car.

"I'm not sure what went on, but probably similar to what happened to Nick. It's not good."

Supercars and Motorsport Australia officials are investigating the cause of the fires.

"The incidents showcased the strong sense of camaraderie and support within the racing community, as teams rallied around each other regardless of whose car was affected," a Supercars official said.

SUPERCARS MELBOURNE SUPERSPRINT RACE THREE

1. Brodie Kostecki (Coca-Cola Racing)

2. Shane van Gisbergen (Red Bull Ampol)

3. Will Brown (Coca-Cola Racing)

4. Chaz Mostert (Walkinshaw Andretti United)

5. Andre Heimgartner (Brad Jones Racing)