As Tropical Storm Isaac moves away from the Gulf Coast and into the country's interior, spinning off tornadoes across two states, the storm has caused its first death in Pearl River County, Miss.
A tow truck driver was killed on the job by a tree that fell around midnight, Pearl River Emergency Management Deputy Director Amanda Harris told ABC News. The man's name and age has not yet been released.
"[The county] is completely flooded. And it's only going to get worse," Harris said, adding that rivers and creeks along the county near the Louisiana border will not crest until midnight tonight through 4 a.m.
"The worst is yet to come," Harris said.
Pearl River County conducted four search and rescue operations and it is believed there are no more residents holding out in their homes, Harris said. The county is receiving assistance from FEMA, state agencies and neighboring counties.
A tropical storm warning is in effect for intra-coastal city Louisiana to the Mississippi-Alabama border, including Lake Pontchartrain and Lake Maurepas.
Lt. Vernon Smith of the Pascagoula, Miss., police tells ABC News that a tornado touched down at 8:20 a.m. just south of town that sits 28 miles from Biloxi.
"It landed right on top of a house, just sat on it," Smith said, adding that people were believed to be inside. "There are people injured."
Smith said the tornado was now off the ground and moving through the main part of town, having traveled about a mile since touchdown. Officials are mobilizing emergency crews, but the torrential rain has made roads impassable, with the 2 to 3 feet of water flooding the area too much for even their emergency vehicles to handle.
"We can't get through and we are scrambling," said Smith.
Surrounding areas of Louisiana are expected to see almost two feet of rain and more dangerous floods by the end of the week, while seven tornadoes have spun off from Isaac in Mississippi and Alabama so far.
A tornado that touched down in Gulfport, Miss., has caused the most damage, where significant destruction to homes has been reported. Carlos Redmond, a spokesman for Harrison County Emergency Management, said it's assessing the damage.
"We're looking for daylight. That's what we're looking for. We'll be able to tell a lot more at that time," Redmond told ABC News Thursday.
The U.S. National Hurricane Center said tornadoes are possible along the central Gulf Coast region and parts of the lower Mississippi Valley through Thursday.
The rising waters from rain and flooding have already left locals scrambling up to attics and onto roofs. The main parishes that pose the greatest concern sit around Lake Pontchartrain. With another 4 to 7 inches of rain expected, many officials have expressed worry about the rising waters.
Officials in LaPlace, La., about 25 miles northwest of New Orleans, in St. John the Baptist Parish, called the situation dire.
"I'm afraid the tide is really going to catch some of us off guard tonight," Parish President Layton Ricks told ABC News late Wednesday night.
Some 3,100 people have been evacuated in the town since 3 p.m. Wednesday, a National Guard officer told ABC News, while more than 1,000 are waiting for rescue in LaPlace as the city sees its worst flooding in 40 years.
Housing developments, such as the River Forest subdivision where dozens of families were rescued Wednesday, are under 5 feet of water. The Louisiana National Guard said it would be out in force Thursday across the St. John the Baptist Parish, assisting in rescue efforts.
"It's our own little Katrina," said Tania Trege, wife of St. John the Baptist Parish Sheriff Mike Trege, describing the situation in Laplace.
Towns southwest of New Orleans have already received about 20 inches of rain, with another 4 to 7 inches possible. New Orleans International Airport has officially received 10 inches of rain so far.
As of 8 a.m. ET, Isaac was about 35 miles southeast of Alexandria, La., and about 125 miles northwest of New Orleans. Tropical storms winds extend outward up to 175 miles. Isaac's maximum sustained winds are at 45 mph, according to the U.S. National Hurricane Center in Miami.
Isaac is expected make a turn toward the north-northwest later today, followed by a turn toward the north on Friday.
A tropical storm warning was still in effect from Cameron, La., to the Mississippi-Alabama state border, according to the Hurricane Center.
An unofficial rainfall total of 22.5 inches was reported in Arabi, La., near the city's 9th Ward on Wednesday. An official report from Audubon Park in New Orleans listed 17 inches of rainfall.
Livingston Parish officials told ABC News that they felt the worst of Isaac at 10 p.m. Wednesday, and expect flooding in the low-lying parts of the parish. Rescue efforts were under way and officials said this will be the first overnight of many water rescues in the area.
Rescue operations are still under way in Plaquemines Parish, where more than 100 people in the parish have been rescued so far. A levee in Plaquemines Parish will be intentionally breached at some point Thursday to relieve pressure on it. That area has been under mandatory evacuation.
More than 725,000 homes and businesses throughout Louisiana were without power as of 2 a.m. Police reported few problems with looting.
In Mississippi, Highway 90 remains shut down, with much of area now submerged in water. 30,000 customers are without power in Gulfport, Miss., alone, where an apparent tornado spawned by the storm ripped a house from ground.
In Biloxi, powerful winds are ravaging the city as residents begin to worry about raw sewage and mold.
President Obama declared federal emergencies in Louisiana and Mississippi late Wednesday, according to a statement from the White House. The disaster declarations free up federal aid for affected areas.
Of Louisiana's 64 parishes, 58 are under states of emergency this morning.
Forecasters expected Isaac to move inland over the next several days, dumping rain on drought-stricken states across the nation's midsection before finally breaking up over the weekend. The storm was expected to weaken to a tropical depression Thursday, according to the Hurricane Center.
Five to 10-foot storm surges were expected in Mississippi and southeastern Louisiana, with seven to 14 inches of rain, and some areas could see 25 inches, the center said.
ABC News' Max Golembo and The Associated Press contributed to this report.