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The State Fair Grounds. Aerials of severe weather flooding in East Baton Rouge Parish on Monday August 15, 2016.

Massive floods moved downriver in south Louisiana Monday, leaving some residents to begin the cleanup process while inundating new areas and forcing more evacuations in a state where an estimated 30,000 people have already been rescued and 12,000 are in shelters.

Officials in two parishes gave rough numbers for how many homes and businesses have been damaged. The total -- even absent any estimate from hard-hit and heavily populated East Baton Rouge Parish -- approached a staggering 50,000.

And the human toll rose to seven with the discovery Monday of an as yet unidentified body near a public library in Baton Rouge.

Rivers across southeast Louisiana, swollen by unprecedented rains that dumped more than two feet in some areas at the end of last week, began to drop in northern Livingston and East Baton Rouge Parish parishes. But as those areas drained, the same water wound its way south into Ascension Parish, swamping new areas, backing up tributaries and leading to fresh road closures and evacuations.

Near Port Vincent along the Amite River in Livingston Parish, convoys of trucks hauling boats barreled toward affected areas, ready to perform water rescues. National Guard trucks prowled the roads, saving people as they went. Similar efforts were underway in nearby Ascension Parish, where officials said 15,000 homes and businesses had been flooded and they were urging some residents to evacuate.

Even where there was warning, many were caught off guard: people in Port Vincent could be seen standing outside their stranded cars as the floods moved in from the north, swelling the Amite and nearby Bayou Manchac.

And to the north in Denham Springs, which saw some of the worst of the flooding, the town remained submerged for the third straight day.

Mark Harrell, director of the Livingston Parish Office of Homeland Security and Emergency Preparedness, estimated that as many as 70 percent of the more than 50,000 homes in the parish have been damaged. New evacuations were being ordered, and rescues were underway in the southern reaches of the parish, he said Monday afternoon.

“They’re pulling out whole subdivisions when they hit it,” Harrell said.

Farther north, however, some residents in the flooded Watson and Central areas were able to return to their houses and begin to assess the damage. As Monday wore on, carpet and furniture began to appear on roadsides, the first step in what for many will be a lengthy cleanup process.

The Louisiana National Guard also signaled a transition away from an active response to efforts focused on recovery, including providing security at area shelters and distribution of bottled water. The Guard had already rescued 7,600 people and 1,200 pets. They had distributed 16,700 meals and more than 200,000 bottles of water, a spokesman said.

But even receding water was still too deep for some in southeastern Baton Rouge near O’Neal Lane, where the level had dropped two feet but residents were still staying away. Some were hopeful that they could return to their homes Tuesday or Wednesday.

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Gov. John Bel Edwards said the flooding was “breaking every record.” The numbers back that up. The Amite River, a main source of the flooding, crested at 46.2 feet near Denham Springs, shattering the previous record by nearly five feet. That continued southward Monday, when it crested at 17.5 feet near Port Vincent, more than three feet higher than its previous record.

The sheer scale and unpredictability of the flooding has stretched state and local resources to their limits, with rescue operations underway from Lafayette to Hammond. Those efforts were complicated by forced closure of more than 280 state roads and innumerable smaller parish roads. Portions of Interstate 12 in East Baton Rouge and Livingston Parish remained closed in both directions, and a 60-mile stretch of Interstate 10 was shut down in southwest Louisiana.

Schools were shuttered across south Louisiana. Tangipahoa and Ascension parishes have closed public schools for the rest of the week. East Baton Rouge and Livingston have said they are closed until further notice. Several other school systems were closed Monday as well.

But there were signs of progress. AT&T reported it has largely fixed problems that cut cell-phone communications for much of Sunday, and Baton Rouge announced a resumption of garbage pickup for Tuesday in neighborhoods where doing so was possible.

So far, four parishes — East Baton Rouge, Livingston, Tangiphoa and St. Helena — had been declared federal disaster areas. Edwards told leaders in several other parishes Monday, including Ascension and Iberia, that he expected that they would soon be declared as well.

From a helicopter, the scale and randomness of the devastation was staggering. In some areas, a street will be flooded, the next street is dry.

Even in dry areas, residents were trapped in their homes when the roads around them were flooded. Roads that on Sunday were open were now submerged, including portions of Interstate 10 southeast of Baton Rouge and Airline Highway, both major arteries.

In other areas, sections of road were inundated while others were clear, stranding motorists on islands and causing jams.

Many in the affected areas do not have flood insurance, but Edwards urged all residents to document any damage. Federal Emergency Management Administration officials are already in the state conducting assessments, he added.

But many people are still just focused on getting to dry ground.

Theresa Gordon fled her Livingston Parish home with her husband.

"We had a house, a church and a snowball stand. It's at least six or seven feet under water now," she said.

Follow Faimon A. Roberts III on Twitter, @faimon.