A fast-moving wildfire 85 miles north of Phoenix has killed 19 of the firefighters who were sent to stop it, according to the Prescott Fire Department and the U.S. Wildland Fire Aviation Service. Earlier, officials had lost contact with 20 firefighters as the blaze spread to Yarnell, Arizona, where it burned at least 250 structures. 

The Prescott Daily Courier reports that the dead made up nearly an entire crew of firefighters, nicknamed the Granite Mountain Hotshots. One crew member got out alive. The Arizona Republic, citing unnamed sources, reported that the survivor has burns over the majority of his body. 

The Yarnell Hill fire, which started on Friday, expanded rapidly on Sunday thanks to high temperatures, windy conditions, and low humidity. Officials still don't know how it started, though it was likely from a lightning strike. The fire is currently at zero containment. 

There's little information on the specifics of the incident that lead to the deaths of so many firefighters, aside from the severity of the entirely uncontrolled wildfire itself. The AP provided the following information, citing a forestry official: 

"Forestry spokesman Art Morrison said the firefighters were caught by the fire near the central Arizona town of Yarnell... he said the firefighters were forced to deploy their fire shelters, tent-like structures meant to shield firefighters from flames and heat."

According to the Arizona Republic, about 250 firefighters were out on Sunday fighting the blaze, with that number increasing to about 400 tomorrow. 

Late on Sunday, the Arizona Republic was running a livestream of coverage of the fire: 

This post on a developing story has been updated with new information.