Detective Sergeant Andrew Raven, of the Warrnambool police crime investigation unit, said detectives spoke with the 16-year-old who was issued with a caution after lighting a fire during Saturday’s high fire danger in the Coghlans Road/Thomas Place area.

It's understood the youth has a fascination with fire trucks and firemen, rather than a fascination with fires.

The fire burnt an area about 20 metres by 10 metres and the Warrnambool Fire Brigade quickly attended and put out the blaze.

Detective Sergeant Raven said on days of extreme fire danger, like Saturday when the mercury topped 40 degrees, such behaviour was extremely dangerous and potentially life-threatening.

"We would request that parents have those conversations with their children, about the danger of fires," he said.

The CIU chief said security camera footage from a nearby house had proved crucial in identifying the youth.

"CCTV is now a relatively cheap security measure for residents that is invaluable as an investigative tool," he said.

The cautioning of the youth comes after a 12-year-old was also cautioned by police for lighting a fire in Bromfield Street on Wednesday last week.

Another 12-year-old has been charged with seven counts of arson relating to lighting fires in Warrnambool public toilets.

Detective Sergeant Raven said the number of youths deliberately lighting fires was a significant concern particularly in mid summer.