Cleanup crews were at work Monday in Ellicott City, Maryland, following dramatic weekend flooding that killed two, swept cars around like driftwood, and destroyed 18th century buildings.

Maryland Governor Larry Hogan declared a state of emergency for Howard County -- located between the US capital and the port city of Baltimore -- on Sunday after powerful thunderstorms ripped through the region late Saturday.

At least two people died when their vehicles were swept away by the flood, Howard County Police Chief Gary Gardner told reporters.

Nearly six inches (15 centimeters) of rain fell within a two-hour period at the height of the storm, the equivalent of a month of normal rainfall, the National Weather Service said.

Hardest hit was historic downtown Ellicott City, founded in 1772 and located near the Patapsco River.

The colossal downpour focused the floodwater on the town, where fast-moving waves lifted cars on top of each other and ripped up roads and sidewalks.

Some 25 buildings and 170 cars were destroyed or damaged, local media reported.

Police evacuated the downtown area and closed it until further notice.

Several cars were left stranded in waist-high piles of mud.

"We've never seen such devastation in Howard County for over 50 years," County Executive Allan Kittleman told CNN.

"In the past, it has been bad. It has never been close to being this bad."

Hogan, who visited the disaster area on Sunday, said that officials "are coordinating all available resources to address this emergency as quickly as possible."