The tornado that tore through northern Illinois Thursday night has received a preliminary rating of EF4 based on an initial ground survey of the most heavily damaged area, the National Weather Service reported Friday evening. “Based on early findings, the tornado that tracked from near Rochelle to near Belvidere and impacted the community of Fairdale appears to have been a single long track tornado,” notes an NWS statement. “An aerial survey will be conducted tomorrow, weather permitting, to confirm a final rating.”

The EF or Enhanced Fujita Tornado Intentisy Scale measures a tornado’s impact. The scale goes from 0 to 5, with 5 being a storm that causes incredible damage. An EF4 tornado brings with it windspeeds of 166 to 200 mph and causes “devastating” damage. Estimated peak windspeeds of Thursday’s tornado reached 180 to 200 mph. (For more on the EF Scale, here is a detailed article .)

Earlier in the day Friday, local officials said they were confident everyone was out of the area. Kirkland Fire Department Chief Chad Connell said they brought in three K-9 teams as a “precautionary measure,” to “double check our work.” Connell said he expected the search-and-rescue portion of the operation to finish before 5 p.m. Central time.

“We think we have everyone accounted for,” added DeKalb County Sheriff Roger Scott. “We have no specific person that’s unaccounted for.”

The area struck yesterday still has no power. Local officials said residents could come to assess the damage to their property on an “escorted basis,” but encouraged people not to stay around until conditions were proven safe.

(MORE: State-by-State Updates on the Severe Weather Outbreak )

Gov. Bruce Rauner earlier in the day Friday declared Ogle and DeKalb counties disaster areas, making state resources available for the areas hardest hit by this storm, which took two lives. Geraldine M. Schultz, 67, and Jacqueline Klosa, 69, next-door neighbors, were both killed, and 11 more people were hospitalized after at least one tornado ripped through northern Illinois Thursday evening at about 7:15 p.m., officials said. Klosa’s body was found during a second search Friday morning , according to the Chicago Tribune .

“Our thoughts and prayers go out to the families impacted. Frankly, we’re very blessed that more people were not hurt; this was a devastating storm,” Rauner said Friday afternoon.

Every home in the community of 200 about 20 miles southeast of Rockford was affected by the storm, authorities said. After crews had a chance to survey the damage in the town, Connell estimated as many as 18 homes were completely swept off their foundations by the large twister.

“It was big. I’ve never seen anything like it in my life,” Connell said of the tornado, according to The Associated Press. Connell watched the tornado move across the area from his front porch.

Matthew Knott, division chief for the Rockford Fire Department, told The Associated Press that 17 structures had been destroyed. “All of the others have sustained damage of some sort.”

“This town is absolutely devastated,” Knott said.

The town’s power was out early Friday, and everyone had been evacuated. A shelter was set up at a nearby high school. The Red Cross and Salvation Army were assisting.

Rescue crews worked quickly, going house to house to look for survivors. That’s when they discovered Schultz’s body in the rubble of her home. “The west side of Fairdale was pretty well destroyed,” Scott, the DeKalb County sheriff, told WLS-TV.

(MORE: 12 Rescued After Restaurant Collapses in Rochelle )

The tornado that hit Fairdale was one of at least two supercell-produced tornadoes that developed, according to weather.com senior meteorologist Nick Wiltgen . A second tornado developed in Cherry Valley at 6:40 p.m. Central time. It’s important to remember that all reported tornadoes are unconfirmed until a survey crew from the National Weather Service views the damaged areas and finds the debris was created by a tornado. However, in the case of the twister that left widespread, severe damage in Fairdale, Rochelle and Kirkland, experts believe it’s a foregone conclusion that it will be confirmed as a tornado. Severe weather expert Dr. Greg Forbes estimated the tornado at a half-mile wide.