SAN ANTONIO (Reuters) – Flooding caused by days of heavy rain forced the closure on Tuesday of a section of a major east-west U.S. highway on the Louisiana-Texas border along the rising Sabine River, officials in both states said.

At least five people have been killed in storms in Southern U.S. states over the past several days that have caused flooding in places including Texas, Louisiana, Mississippi and Arkansas, forcing thousands of people to flee homes caught in floodwaters.

The closure of the section of Interstate 10 was forcing drivers to take lengthy detours of up to hundreds of miles to traverse the flood-soaked region.

Flooding along the Sabine River that separates Texas and Louisiana has forced the evacuation of hundreds of people from their homes. Texas Governor Greg Abbott late on Monday issued a disaster declaration for 17 eastern and southeastern Texas counties.

In Louisiana, state officials said more than 6,000 structures had been damaged by flooding across the state, and new problems were being reported in some areas as rivers continued to rise.

Since last Wednesday, the Louisiana National Guard has rescued more than 4,200 people while the state’s Department of Wildlife and Fisheries has rescued another 700 people.

The hardest-hit parts of Texas have been in the southeastern part of the state, where “dozens if not hundreds” of high water rescues have taken place, according to Emergency Management Coordinator Billy Smith.

“It will probably be several days before it crests,” Smith said of the floodwaters, adding that the Sabine River is expected to crest at a level higher that the previous record set in 1882.

In eastern Harrison County in Texas, sheriff’s office Lieutenant Jay Webb said the high waters have raised worries about alligators.

“The nature of alligators is they don’t want to stay in water,” Webb said. “They want to be on higher ground with access to water. With flood levels porch-high, those alligators may be on somebody’s back porch.”

Authorities described the flooding as some of the worst in the region apart from that spawned by hurricanes. President Barack Obama on Sunday declared the flooding in Louisiana a major disaster, activating federal aid.

(Reporting by Jim Forsyth; Additional reporting by Colleen Jenkins in North Carolina; Writing by Jon Herskovitz; Editing by Will Dunham)