BARABOO, Wis. -- Widespread flash flooding in the Baraboo area forced last-minute evacuations on Thursday night.

VIDEO: Wisconsin Ducks Rescue Baraboo Residents From Flooding | READ: Notebook: Chasing Storm, Story In Baraboo | SLIDESHOW: See Photos Of Wisconsin Ducks Rescuing Stranded Residents

Baraboo city officials said that about 30 people stayed overnight in a downtown shelter at the courthouse.

With few roads that will get people in or out, one official said that the city of Baraboo is almost like an island.

Earlier in the afternoon, Sauk County authorities sought the help of the Original Wisconsin Duck boats from two Wisconsin Dells companies that typically provide scenic tours of area waterways. Eleven of the amphibious, World War II-era vehicles were used to make more than a dozen rescue missions from dusk until dark, bringing about 100 people to safety, WISC-TV reported.

Officials estimate at least a dozen Duck loads of people were brought to safety

Five agencies, including Lake Delton authorities, assisted in the Baraboo rescue efforts. Many of those rescued were reunited with family or friends who agreed to take them in for the night.

Many roads in the Baraboo area and all around Sauk County are impassable and remain closed after rushing water ran over the top of them, in many cases washing away the roadway.

Raging floodwaters raced into Baraboo on Thursday afternoon, moving past the Circus World Museum, cutting its own path and letting nothing get in its way.

Tim Stieve, with Sauk County Emergency Management, said that he considers the flooding in the Baraboo area to be worse than what was seen during the floods of 1993.

"It's just devastating for this entire area to see this happen to it," Stieve said.

Emergency management officials say it will take days to assess the damage, but first they need the rain to stop.

No injuries have been reported.

Jeff Jelinek, of Sauk County Emergency Management, said that the extent of the flooding is greatly affecting those seeking to help the victims.

"It's starting to take a toll I think on everybody," he said. "Everybody's been putting in long hours and it just seems like we're back to square one again."

The brown-colored floodwaters contained sand from the nearby Baraboo River and deposited silt throughout the area.

Cars were swept out of their driveways and into each other. Many are now stuck in mud.

Residents are being warned that floodwaters are highly contaminated, not only with debris, but also raw sewage. People should stay out of the water when possible, and never enter water where you are unsure of the depth or speed that it may be moving, officials said.