A wildfire burning in Grand Canyon National Park triggered a chlorine gas leak Friday afternoon after flames reached a water treatment facility.

Visitors and staff at two national parks in the U.S. West have been evacuted because of wildfires. Officials at Black Canyon of the Gunnison National Park in Colorado say the park closed Thursday morning after lightning sparked blazes on both rims.

Authorities increased the size of the evacuation zone for the White Sage Fire north of the Grand Canyon on Friday morning.

The Coconino County Sheriff's Office helped evacuate people from an area north of Jacob Lake and campers in the Kaibab National Forest nearby.

A mix of high temperatures, gusty winds, low humidity, and dry vegetation has fuelled the fire's swift advance, officials say.

The North Rim of the Grand Canyon is closed "until further notice" as a wildfire rages in the area, park rangers announced on Thursday.

Officials evacuated Jacob Lake and the North Rim of the Grand Canyon was closed to visitors because of the fast-moving White Sage wildfire.

Hundreds of visitors and residents were evacuated from the North Rim of Grand Canyon National Park this week as two wildfires advanced toward the park.

A 63-year-old woman was found a quarter mile away from her vehicle. The investigation indicated she was returning to the trailhead when she collapsed.