A pair of rapidly growing wildfires in northern Arizona that have prompted evacuations and forced parts of Grand Canyon National Park to close temporarily continued to burn uncontained today NZT.

The bigger of the two, the White Sage Fire, originated last Thursday about 24km southeast of Fredonia, Arizona, after a thunderstorm moved through the area, according to the United States Bureau of Land Management.

As of today it had burned more than 16,190ha near the unincorporated community of Jacob Lake, and firefighting efforts had not achieved containment.

“The fire continues to exhibit extreme behaviour, being driven by steady winds in very hot and dry conditions,” federal authorities said in an update.

Forecasts of strong “gusty and variable winds” combined with low relative humidity mean large fire growth is expected to continue, the Bureau of Land Management said in a report on the White Sage Fire.

The National Park Service last Friday had evacuated all visitors and campers at the North Rim of Grand Canyon National Park due to the White Sage Fire, which was burning about 50km from the Dragon Bravo Fire.

The Dragon Bravo Fire had burned more than 2025ha, and was sparked on July 4 as a result of a lightning strike in the park, federal authorities said.

“The Dragon Bravo Fire on the North Rim of Grand Canyon National Park grew quickly overnight, jumping over several fire control lines,” the National Park Service said in an update yesterday. There are no reports of injuries or loss of life, it added.

In addition to the North Rim, the North Kaibab Trail, the South Kaibab Trail and the Phantom Ranch area were also closed until further notice due to concerns about a potential chlorine gas leak related to the fire, the Park Service said. The South Rim remains open and operational, it added.

Coconino County authorities “have issued evacuation notices for areas north and south of Jacob Lake and the North Rim of the Grand Canyon National Park,” the Bureau of Land Management said.