CNN — The mammoth flood engulfing a Massachusetts city – both from epic rainfall and from water gushing downhill – could get more disastrous as officials evacuate homes near a “very sensitive” dam.

Already, some basements in Leominster “probably have feet of water inside of them,” and “we have several homes where the water washed out … you can see the foundation of the home,” Mayor Dean Mazzarella said Tuesday morning.

“We had to evacuate people last night … with hovercrafts and boats to get people out to safety,” the mayor said.

“Hospitals went down with no power last night, several nursing homes, several areas of town,” he said. “Downtown was completely flooded.”

The calamity unfolding in Leominster – a city of about 44,000 people northwest of Boston – started when roughly 11 inches of rain pummeled the city in just six to seven hours late Monday, the mayor said.

And the topography made the disaster even worse.

“Leominster is about 26 square miles. We have 12 hills, and obviously from those hills comes the water,” the mayor said. “And with 11 inches of rain, it just adds to the … water (going) downhill.”

Realizing the situation was turning “catastrophic,” Mazzarella said, “we declared a state of emergency here in the city and called in all police, fire, emergency management.”

The Massachusetts Emergency Management Agency is urging some residents to evacuate due to “a potential issue at the Barrett Park Pond Dam,” MEMA said on X, formerly known as Twitter.

“This particular dam is one that we’re actually about to replace,” Mazzarella said. “It is very sensitive. It’s water saturated. And we’re worried about that downstream. So, we’ve put out a code red and notified everyone along that stream bank, along that river base … to evacuate.”

And it’s not clear when children will be able to go back to school.

“Today, our schools are closed,” the mayor said. “We have a couple of schools that experienced severe damage and flooding. And the other schools are open for shelters.”

The deluge has also washed away roads and created a large sinkhole, Mazzarella said.

“That was the road … it’s gone,” the mayor said in a Facebook video showing the massive sinkhole.

Videos posted on social media show vehicles submerged by dark flood waters on a highway. Other footage shows emergency vehicles trying to navigate a street overtaken by rapidly moving water as rain continues to fall. Another video shows water filling a gaping sinkhole in the middle of a street lined with houses.

While the rain has largely subsided in Leominster, “it’s going to take a while for the rivers to reach their peak,” Mazzarella said Tuesday morning.

And more rainfall could thrash Massachusetts and northern New England this weekend, depending on the track of Hurricane Lee.

CNN’s Sara Smart, Monica Garrett, Derek van Dam, Amanda Jackson and Melissa Alonso contributed to this report.