ATLANTA, June 20 (AP) - Tropical depression Claudette claimed 12 lives in Alabama as the storm swept across the southeastern US, causing flash flooding and spurring tornadoes that destroyed dozens of homes.

Ten people, including nine children, were killed on Saturday (Jun 19) in a fiery multi-vehicle crash about 55 kilometres south of Montgomery on Interstate 65, according to Butler County Coroner Wayne Garlock.

He said the vehicles likely hydroplaned on wet roads, with eight children, ages four to 17, killed in a van belonging to a youth ranch for abused or neglected children operated by the Alabama Sheriffs Association. Two people died in separate vehicles, Garlock told local news outlets - 29-year-old Cody Fox and his nine-month-old daughter, Ariana, both of Marion County, Tennessee.

Multiple people were also injured.

The National Transportation Safety Board tweeted that it was sending 10 investigators to the area on Sunday to investigate the crash, which photos showed included at least four burned vehicles, including two large trucks. It said the inquiry would focus on vehicle technologies such as forward collision warning systems, fuel tank integrity and occupant survivability.

Meanwhile, a 24-year-old man and a three-year-old boy were killed when a tree fell on their house just outside the Tuscaloosa city limits on Saturday, said Captain Jack Kennedy of the Tuscaloosa Violent Crimes Unit.

The deaths occurred as drenching rains pelted northern Alabama and Georgia late Saturday. As much as 30cm of rain was reported earlier from Claudette along the Mississippi Gulf Coast.

Flash flood watches were posted on Sunday for northern Georgia, most of South Carolina, the North Carolina coast, parts of southeast Alabama and the Florida Panhandle. A tropical storm warning was in effect in North Carolina from the Little River Inlet to the town of Duck on the Outer Banks. A tropical storm watch was issued from South Santee River, South Carolina, to the Little River Inlet, forecasters said.

Top winds from Claudette remained near 45kmh on Sunday. National Hurricane Center forecasters predicted it would strengthen back to tropical storm status Monday over eastern North Carolina before heading out to sea in the Atlantic Ocean.

The center of Claudette’s disorganised circulation was located about 15km west-southwest of Athens, Georgia, on Sunday afternoon. It was moving east-northeast at 28kmh, the National Hurricane Center said.