At least four people have died in Texas after Tropical Storm Imelda brought catastrophic flooding to the region on Tuesday, and hundreds of residents remain displaced from their homes.

The body of a 47-year-old man was found Friday in a Toyota Prius after waters from a flooded canal receded. Another man's body was found in a ditch on Friday afternoon; the unidentified man likely drowned, officials said.

A 19-year-old man also drowned and was electrocuted while trying to move his horse during a lightning storm on Thursday, according to the Jefferson County Sheriff's Office.

And a man thought to be in his 40s or 50s drowned while trying to drive a van through eight-foot floodwaters on Thursday afternoon near the George Bush Intercontinental Airport in Houston, Harris County Sheriff Ed Gonzalez said.

Imelda was one of the wettest tropical cyclones in U.S. history. More than 40 inches of rain fell in southeast Texas over four days, ending by Thursday night, the National Weather Service (NWS) said. Floodwaters finally began to recede on Friday.

TEXAS HIT BY IMELDA DELUGE, FLASH FLOODS, 'LIFE-THREATENING' RAINFALL: 'IT'S AS BAD AS I'VE EVER SEEN'

"Moisture associated with what was once Tropical Depression Imelda will still bring heavy rain and scattered localized areas of flash flooding to portions of the Southern Plains," the NWS said. "A slight risk of excessive rainfall is in effect, where one to three inches of rain [are] forecast."

There were at least 1,700 high-water rescues and evacuations in Harris County, officials said.

A nursing home in Porter, northeast of Houston, evacuated 87 residents, according to a Montgomery County Office of Emergency Management spokeswoman. No injuries were reported from the evacuations.

"The issue is that you can’t get 40 inches of rain in a 72-hour period and be fully prepared for that,” Jefferson County spokeswoman Allison Getz told The Associated Press. "At this point we haven’t been able to fully assess what’s happened."

Much of Jefferson County is still "greatly impacted," the sheriff's office said Friday, while asking residents to stay off the roads.

Interstate 10 was completely closed Friday morning when two barges hit the bridges over the San Jacinto River. More than 900 flights were delayed or canceled in Houston as of Thursday due to the storm.

The Texas Military Department said the state's National Guard had evacuated 739 people and completed 130 rescues.

"We will always be there when you need us," it said.

Gov. Greg Abbott declared a state of emergency in 13 counties.

“The state of Texas is working closely with local officials and emergency personnel to provide the resources they need to keep Texans safe from Tropical Storm Imelda,” Abbott said. “I thank our first responders who are acting swiftly to help the communities that are facing this severe weather event. I urge all those in the path of this storm to take the necessary precautions and heed all warnings from local officials."

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The Associated Press contributed to this report.