Two raging wildfires have threatened the Arizona city of Flagstaff and forced homes to be evacuated.
Hundreds of firefighters have been battling the blazes, the larger of which has burned close to 9,000 acres.
Residents of several hundred homes remain under evacuation orders. No serious injuries or property damage have been reported.
A man was arrested in connection with the smaller fire, after police said he left behind hot coals in a campfire.
The cause of the larger fire was unknown, but officials said it had been spread by strong winds up to 50mph (80km/h).
Low humidity and high temperatures have also contributed to the spread of the blaze, which broke out on Sunday.
"The fire is torching and crowning, with fire burning at the top of the tree canopies," Flagstaff city spokeswoman Stephanie Smith told the Arizona Republic newspaper.
'The Schultz fire'
The larger blaze, dubbed the Schultz fire, moved within 450 metres (500 yards) of some homes, fire spokesman Eric Neitzel told the AP news agency on Monday.
The Schultz fire has also approached US Route 89, a road which leads to the Grand Canyon National Park. Officials are now concerned the fire could leap across the road.
Firefighters built a containment line overnight on Sunday between the forest and local communities. They have also begun digging trenches and clearing out brush from around homes said Mr Neitzel.
Five helicopters and eight air tankers aided ground crews on Monday by dropping fire suppression chemicals.
Arizona's "fire danger" rating is considered high to extreme. The state has already seen two wildfires burn more than 3,000 acres each in June.