Marion County Coroner Jerry Richardson tells The Associated Press two deputies were transporting the women between Nichols and Mullins night.
He added the women, who he says were not detainees but mental health patients, were not strapped/shackled in the van.
Responders congregate on September 19, 2018, near where two people drowned Tuesday evening when they were trapped in a Horry County Sheriff transport van while crossing an overtopped bridge over the Little Pee Dee River, in Marion County, S.C. Doors to such areas don't typically open from the inside.
Chief Deputy Tom Fox said the van was overtaken by water about ½ mile from the Little Pee Dee River. They were going down Highway 76 when the floodwaters began to rise near the Little Pee Dee River, which is a branch of the Lumber River.
"There are barriers there", Richardson said.
The South Carolina Law Enforcement Division is reportedly investigating the circumstances surrounding their deaths.
Bishop and Flood have been placed on administrative leave while three separate investigations are conducted into the deaths. High-water rescue teams plucked the deputies from the top of the van.
Thompson said neither deputy had committed any significant past driving infractions in connection with their duties.
In a statement to the media outlet, the Sheriff's Office says that "despite persistent and ongoing efforts", the sheriffs weren't able to free the women inside.
They've been using high-water vehicles and other equipment to rescue dozens of people.
U.S. Northern Command said the troops will stay until they're no longer needed.
Dive crews were still working at the scene around noon Wednesday to recover the van, which officials say was swept off a rain-soaked road at around 6 p.m. Tuesday.
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. The sheriff's office transports 1,200 patients per year, traveling up to 40,000 miles each month, he said.
US President Donald Trump visited storm-ravaged North Carolina on Wednesday, while the state's governor, Roy Cooper, pleaded with thousands of evacuees not to return home just yet, warning the flooding is far from over and will get worse in some places.
The paper reported that a therapist chose to commit Green, a mother of four, after she showed up for a counseling session on Tuesday morning.