The death toll from Florence reached at least 37 in three states Tuesday, as Florence went in two directions: Water flowed downstream toward the Carolina coast, and storms hit the Northeast, where flash floods struck New Hampshire and NY state.
The deputies waited on top of the van until rescuers arrived.
Thompson identified the women as Windy Newton, 45, and Nicolette Green, 43.
"Tonight's incident is a tragedy", Horry County Sheriff Phillip Thompson said in Tuesday's statement. Thompson said neither deputy had committed any significant past driving infractions in connection with their duties.
"We want those who are responsible to be held accountable", it reads in part.
The coroner in neighboring Marion County confirmed the two deceased patients were female, and the South Carolina State Law Enforcement Division is investigating the incident, according to the statement. Officials said the van was in Marion County near the Little Pee Dee River, one of the bodies of water state officials are watching closely after Florence.
Two women "detainees" chained in the back of a police van died when the vehicle was engulfed by Hurricane Florence floodwaters. The two individuals being transported were confirmed dead by the Marion County Coroner.
"The two deputies attempted to extricate the persons being transported".
"They're still under the water", he said.
Holden said that deputies tried to get the victims out but couldn't. At almost 7 p.m. Wednesday, State Law Enforcement Division spokesman Thom Berry confirmed the bodies had been recovered.
The patients were being transported from Loris Hospital Waccamaw Center for Mental Health to McLeod Health, which runs multiple facilities in the region, according to WPDE.
President Donald Trump on Wednesday visited North Carolina, which is bearing the brunt of Florence's deadly deluge and where rivers are still rising while thousands of homes and roadways remain submerged.
The death toll from Florence rose to 37 in three states, the AP report noted.
Prisoners in SC were pictured filling sandbags after officials refused to evacuate them to safety from storm Florence.
"I'm not sure if it was the way the van was positioned, against a guardrail, or if it was pressure from the water, but unfortunately they were not able to get the van doors open and get the ladies out", Thompson said.