By Rich McKay

(Reuters) -The weekend flooding in Tennessee that killed at least 21 people was more destructive than originally estimated, with about 120 homes washed off foundations, destroyed or simply “gone,” officials said Tuesday.

The scope of the damage came into sharper focus in hardest hit Humphreys County, as rescue teams continue to search house-to-house with trained dogs for dozens believed still missing.

“Our damage is much more massive than what we thought,” Humphreys County Sheriff Chris Davis told NPR in an interview Tuesday.

It was already believed that hundreds of homes were water-damaged and uninhabitable, officials said after the storm brought 17 inches of rain in just three hours.

Davis and other officials surveyed the damage from a helicopter late Monday, focusing largely on the hardest hit town of Waverly, about 55 miles west of Nashville.

“Yesterday we thought it was 20-something houses that had been removed from the foundations,” Davis said. “That’s not even close. Well over 100 – 120 houses have been moved, or are gone, no longer exist.”

Displaced residents found shelter with relatives, local churches and with housing provided by the American Red Cross, the sheriff said.

Officials who had been seeking federal aid were granted it late Monday as President Joe Biden declared a major disaster in the state of Tennessee and ordered federal aid, the White House said in a statement.

Local officials said that those killed in the flooding ranged in age from babies to the elderly. The Washington Post, citing family members, reported that 7-month-old twins died after they were swept away from their parents’ arms.

(Reporting by Rich McKay in Atlanta and Bhargav Acharya in Bengaluru; Editing by Kim Coghill and Chizu Nomiyama)