The California Rim Fire now encompasses an area of 280 square miles along the western edge of Yosemite National Park, making it the seventh-largest wildfire in California history.

According to the California Department of Forestry and Fire Protection (CAL FIRE), the Rim Fire now stands at 20 percent containment, the same figure as Monday night. Earlier on Monday, the fire stood at 15 percent containment and at 7 percent throughout Sunday. Still, more than 5,500 structures are considered threatened, and at least 111 have already been destroyed, including 31 residences. Also threatened are two groves of giant, ancient sequoia trees northwest of the fire.

A team of more than 3,700 firefighters has been working tirelessly to stem the advancing flames. Cal Fire spokesman Daniel Berlant told the Los Angeles Times that firefighters have been strategically burning and bulldozing vegetation on the fire’s perimeter to keep the Rim Fire from advancing on homes near California Route 108.

“We’ve burned back down the mountain so that if the fire makes the river, jumps the river, that side of the hill is already burned,” he said. “We’re coming around the corner, catching the western portion of the fire and we’ll continue to pinch it off as it goes up to the northern flank.”

It seems unlikely that the Rim Fire will abate anytime soon. The fire grew 19,000 acres from Monday to Tuesday, and 16,000 acres in the previous 24 hours.

“It’s burning its way into the record books,” Berlant added.

As the fire continues to grow, it poses a major threat to the San Francisco Bay Area, located roughly 150 miles away. The San Francisco Chronicle reports that on Tuesday, the Rim Fire hit the shores of the Hetch Hetchy reservoir, the Bay Area's primary source of water. Gov. Jerry Brown has already declared a state of emergency over the fire’s threat to water reservoirs.

Officials at the reservoir, however, assured reporters that the 2.6 million Bay Area residents are in no immediate danger. Water from the Hetch Hetchy remains potable, and other reservoirs are capable of providing water in the event that it is contaminated. Additionally, workers have begun shifting water away from the Hetch Hetchy into other locations. Public Utilities Commission General Manager Harlan Kelly Jr. said a recent expensive upgrade to the city’s piping system had also helped to safeguard the city.

Kelly said San Francisco currently has a six-month back up water supply. Brown’s emergency declaration on Thursday, which referenced “conditions of extreme peril,” also permitted the city to spend $600,000 on replacement electricity, Bloomberg reports.