Officials said a large wildfire that has burned all week in southern Arizona has cost more than $4.25 million to fight so far, according to a report from the Arizona Daily Star.

Some 800 personnel have been assigned to the so-called Sawmill fire, which has burned more than 73 square miles and was 40 percent contained as of Friday afternoon. Pilots spent much of Friday morning dumping water on the blaze from above, but as winds picked up again, all airplanes and helicopters were grounded.

Pre-evacuation orders remained in place for hundreds of homes in desert areas near Interstate 10, said Manny Cordova, spokesperson for the interagency team managing the firefighting effort, in an Associated Press report. The wildfire is about 10 miles away from hundreds of homes, all of which are in rural areas near the interstate.

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Due to the increasing complexity of the blaze, management of the blaze transitioned to a Type I Incident Management Team Thursday, Inciweb reported. This essentially means the fire is being treated as a natural disaster, KVOA.com said.

"Precipitation has been below average in this area for the last few months," said Dolce. "Green Valley has seen just 0.43 inches of precipitation since Feb. 1 – about 25 percent of their average for that period."

The blaze started southeast of Green Valley Sunday, near the Santa Rita Mountains. It was sparked by an off-duty Tucson Sector Border Patrol agent who was shooting recreationally, authorities said Thursday.

No injuries or structural damage have been reported.

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