WASHINGTON - Storms sweeping across southern US states killed at least five people on Monday, officials and news reports said.

Four people were killed in Alabama when a tree crashed onto their mobile home, the state governor said.

In Florida a man was found drowned near his flooded vehicle in Mossy Head on the Gulf coast of Mexico, the Weather Channel reported.

It said numerous tornadoes touched down and tens of thousands of customers were left without power in Texas and Louisiana.

The victims were in a mobile home in Rehobeth, just outside the city of Dothan, Houston County emergency management spokeswoman Kris Ware said in a telephone interview.

Authorities fighting to extricate three more people who were in the mobile home at the time expect them to survive, but emergency workers are trying to determine how badly they were hurt, she added.

"Prayers for those impacted today," Alabama Governor Robert Bentley said in a message on social network Twitter, referring to the four deaths.

The National Weather Service has made a preliminary determination that a tornado struck the area, Storm Prediction Center meteorologist John Hart said by telephone.

Ware said officials believed the four mobile home deaths were due to a tornado, adding that the roofs and garages of other homes nearby also suffered damage.

Officials said they plan to make a full damage assessment on Tuesday.

The National Weather Service had a total of six preliminary reports of tornadoes touching down in Alabama and Mississippi on Monday, Hart said.

Except for Rehobeth, there were no reports of fatalities from the possible twisters, however.

Heavy rains brought by the storm system caused localized flooding in some parts of the US South, officials said.

A 70-year-old man in the area of DeFuniak Springs in northwest Florida was found drowned on Monday following flooding there, the Walton County Sheriff's Office said in a statement.

Sheriff's deputies discovered the man facedown near his partially-submerged car, it added, but it was not immediately clear when he drowned.

Strong winds snapped power lines in several US states along the Gulf of Mexico coast on Monday, leaving tens of thousands of customers without power, officials said.

Hail fell in several states, including Alabama and Arkansas, the National Weather Service said.

The weather in the US South was expected to improve on Tuesday, Hart said.

The storms had limited impact on air travel, with nearly 40 arriving and departing flights canceled at Houston Bush Intercontinental Airport, one of the country's busiest, according to tracking firm flightaware.com.