SAN FRANCISCO -- Dozens of residents remained evacuated Monday after a weekend lightning storm sparked multiple wildfires around Northern California.More than 600 firefighters were trying to protect 100 structures from the blazes in northeastern Shasta County. No injuries had been reported in that county.Crews also were fighting blazes in Lassen, Monterey and Tuolumne counties.The largest fire was a 4,600-acre blaze burning in Stanislaus National Forest in Tuolumne County, where firefighters have struggled in steep, rugged terrain, said CalFire spokeswoman Nancy Longmore.Three people have been injured since the fire began July 26. One firefighter among the more than 1,300 battling the blaze broke his foot, the most serious of the injuries, Longmore said.Crews helped by low temperatures, relatively calm winds and high humidity had the fire 40 percent contained, she said."If we can get through today without anything going awry, then we're going to be in very good shape," Longmore said.The cause of the fire was under investigation.Lightning was being blamed for dozens of wildfires that started Saturday night and early Sunday, according to California Department of Forestry and Fire Protection spokeswoman Tammy Hay.In Shasta County, 160 miles north of Sacramento, fires burned more than 1,000 acres and were about 10 percent contained.Emergency officials ordered a mandatory evacuation Sunday for the community of Sam Wolfin Springs, while a voluntary evacuation was called for Big Eddy Estates.Fire officials said the blazes in Shasta County were 10 percent contained. Twelve fires in that complex had been contained and crews were still fighting 23 blazes.A 1,500-acre fire was burning in Lassen National Forest along Highway 89, which prompted a stretch of the road to be closed.Crews have also contained more than 60 percent of a 1,600-acre fire in Lassen County. That fire was expected to be fully contained by Friday.------Associated Press Writer Judy Lin contributed to this report.