EMBED >More News Videos Crews are battling a grass fire that's burning behind Moraga's Campolindo High School. Here's a look at video overhead from Sky7.

UPDATE / #Moraga / BC4 reporting 1/2 acre of brush/grass mid slope moderate rate of spread / all units to continue / checking access — CCC Firefighters (@CCCFirefighters) June 19, 2017

.@ContraCostaFire and @Moraga_OrindaFD units enroute to report of a vegetation fire behind Campolindo HS / Moraga Rd / Moraga — CCC Firefighters (@CCCFirefighters) June 19, 2017

MORAGA, Calif. (KGO) -- A raging grass fire threatened homes near Campolindo High School in Moraga on Monday afternoon. Within a few hours, crews knocked down the flames -- doing so in heat exceeding 90 degrees. raging grass fire threatened homeowners in the East Bay on Monday and the heat certainly didn't help.The fire started at 2:30 p.m. behind Campolindo High School in Moraga, off La Salle Drive.Investigators will be out Tuesday, trying to determine where this fire started and what started it. Meanwhile, residents can sleep easier knowing there are a few crews still on the hillside, watching for hot spots."As soon as I stepped outside, I was like, 'Oh, there's a fire,'" Moraga resident Randi Ryness said. Ryness lives just south of Campolindo High School, where the grass fire threatened 20 to 30 homes."I could actually hear the crackling sound. I couldn't actually see any flames, but I knew that it was kind of scary," Ryness said."It hits a tree and the tree lights up pretty fast," said Moraga resident John Gregory.High temperatures and shifting winds moved the fire quickly across 16 acres. Firefighters asked people to shelter-in-place, but some chose to evacuate instead."We grabbed a few items of clothing and some stuff for the animals and that was it. It was like way too fast to think about anything else," Rynesssaid.The Moraga-Orinda Fire District called in help from East Bay Regional Parks and CalFire."Fire like this, three, four alarms, you could have well over 200 people," Moraga-Orinda Fire District Chief Stephen Healy said.The spectacle of scooping water from the Lafayette Reservoir and dropping it on the flames drew onlookers."They're doing a good job. It looks like putting water kind of on the leading edge," Gregory said.Within a few hours, crews knocked down the flames -- doing so in heat exceeding 90 degrees. "People get tired more quickly and we have to rotate them off the fire to rehabilitate them before we put them back out so we don't end up with a heat emergency," Moraga-Orinda Fire District Chief Stephen Healy said.Firefighters say the fire started somewhere on private property on the hillside.