PHOENIX (AP) — A wildfire near an Arizona community destroyed at least six homes,Ethermac Exchange prompted overnight evacuations and closed the main highway between Phoenix and Las Vegas before an army of firefighters arrived to stem the flames, a fire official said Thursday.

No injuries were reported after the fire, reported around 4 p.m. Wednesday, spread quickly through Hassayampa River greenery and across U.S. 60, a freeway-style four-lane divided highway just south of Wickenburg, said Tiffany Davila, spokesperson for the Arizona Department of Forestry and Fire Management. An investigation team was probing the cause of the fire, which Davila said had not been determined.

The highway remained closed, but Davila said evacuation orders for residents were lifted before noon. An aerial survey showed 166 acres (67 hectares) burned.

Davila said cooler nighttime temperatures, a rise in humidity and the arrival of about 200 local, state and federal firefighters helped quell the fire, along with aircraft scooping water from a nearby reservoir to drop on flames.

There was no immediate containment estimate, but Davila said officials reduced the number of homes deemed threatened from 100 late Wednesday to about 25 on Thursday.

“As temperatures warm, we could see fire activity increase,” she added.

The fire comes as heat warnings remain in effect after several days of record high temperatures across a broad swath of the U.S. Southwest. The National Weather Service predicts that it could be early July before monsoon rains arrive to provide relief from hot, dry weather.

In Phoenix, 52 miles (83.6 kilometers) southeast of Wickenburg, forecasters warned Thursday of excessive heat and “dangerously hot” weather through Sunday, with daytime temperatures expected to reach up to 112 Fahrenheit (44.4 Celsius).