A 56-year-old Perth police officer has been charged by summons over a bushfire that destroyed 72 properties.

Robert James Stevens from Roleystone has been charged with carrying out an activity in the open air that causes or is likely to cause a fire.

It is understood sparks from an angle grinder the sergeant was using during a total fire ban started the blaze.

Stevens is on leave and was off duty at the time. It is also understood his wife is ill.

He is due to appear in court next month. If convicted he faces a maximum penalty of $25,000 and a year in jail.

Earlier, police said they had been unable to contact Stevens since Monday when evidence was seized from his home.

The damage bill from the fire is expected to stretch into the tens of millions of dollars.

Meanwhile, Emergency Services Minister Rob Johnson says people in the Perth hills were notified as quickly as possible about the bushfire.

It has been revealed that alerts were only sent out after properties were already under threat.

Fire authorities say they initially thought the blaze was contained and did not send an alert to the public or the media.

When they did it was a bushfire advice, the lowest warning level.

Mr Johnson has defended the system.

"Some of those people who were very close to the fire would get the state alert probably within an hour-and-a-half or so of the fire actually starting," he said.

"That's better than we've had in the past. It may not be the best but we're certainly working on that."

Fire authorities say there will be a full public investigation into the timeline of the fire.

The State Opposition has called for an independent investigation.