This car is inundated Sunday by flooding in New Orleans. In Mississippi, Gov. Phil Bryant tweeted that he had signed a state of emergency declaration for all areas of his state affected by heavy storms.

NEW ORLEANS — Mississippi authorities rescued a man clinging to a tree as heavy rains caused flooding in the state and in neighboring Louisiana.

New Orleans residents awoke to flooded streets Sunday and the Mississippi Highway Patrol closed part of a highway due to heavy rains that also may have contributed to a freight train derailment.

A flash flood warning was extended for New Orleans and surrounding parishes into Sunday afternoon as strong storms with heavy rain moved through the area. Photos published in Nola.comThe Times-Picayune showed partially submerged vehicles and people wading through ankle-deep water.

Mississippi Gov. Phil Bryant tweeted on Sunday that he had signed a state of emergency declaration for all areas affected by the storms.

The Sun-Herald reported that first responders worked overnight from Saturday into Sunday, sometimes using boats, to rescue people in northern Harrison County in Mississippi.

County Fire Chief Pat Sullivan told the newspaper that one man was clinging to a tree after floodwaters swept his car off a road and another man and his 4-year-old child were rescued from the roof of their submerged pickup truck.

Sullivan, like authorities in other affected states, urged people to use caution and not to drive through floodwaters.

Flooding caused the Mississippi Highway Patrol to close part of Highway 49 in Stone County Sunday morning, and dozens of residents in Stone and Pearl River counties were forced from their homes by high water, news outlets reported. The flooding may also have contributed to the derailment of a freight train near Lumberton a little after 7 a.m. Saturday.

The derailment, in Pearl River County, happened as the train traveled from Birmingham, Ala., to New Orleans, said Norfolk Southern spokesman Rachel McDonnell Bradshaw.

Three of the cars were carrying steel and 25 were empty, Bradshaw said. She said no hazardous materials were involved and no injuries were reported. The cause of the derailment is under investigation, but WLOX-TV quoted authorities as saying the roads near the derailment were flooded over.