First responders searched homes and buildings on Tuesday for possible victims of a powerful tornado that ravaged several north-eastern Wisconsin communities.

The Fox Cities region, which is home to more than 100,000 people in the cities of Appleton, Menasha and Neenah, was left in shambles by Monday’s twister, with homes leveled, cars flipped and power lines and trees toppled.

“The depth of the tornado and its impact is incredible, devastating. We’re really still at the assessment stage,” the Winnebago county executive, Gordon Hintz, said at a news conference on Tuesday.

David Chew, 55, said a tree smashed through his roof in Menasha, and he still hadn’t located an outdoor patio lounger swept away by the storm. But he is better off than a neighbor: a portion of her roof was ripped clean, with furniture and drywall “sucked out”.

“It was just a shocker,” said Chew, who had rushed to the basement with his wife and son.

Despite widespread damage, the timing of the storm could be why there have been no reported deaths. The tornado arrived in the early afternoon, authorities noted, when most people were awake and after warnings had been issued.

“Everybody was at work. It was the middle of the day,” Menasha’s police chief, Matt Albrecht, said. “Most people were not at home and at their place of employment.”

Dozens of people were injured, and officers were still going door-to-door a day later in search of possible victims.

The tornado touched down around 1pm and remained on the ground for more than 20 minutes, cutting a roughly 12-mile (19km) path of destruction, the National Weather Service reported. The area is about 100 miles north-west of Milwaukee.

Governor Tony Evers declared a state of emergency for the affected areas. Shelters were opened for displaced residents.

As chainsaws roared in the background, Appleton’s mayor, Jake Woodford, said a number of neighborhoods were “truly devastated”. Like elsewhere in the region, electricity lines were tangled around broken trees, making power restoration a slow, risky process.

More than 10,000 customers in Winnebago and Outagamie counties were still without power, according to utilities that serve them. It could be several days before power is fully restored.

The twister was spun off by a large storm system that moved through the Great Lakes and was fueled by a buildup of heat and humidity, the weather service said.