Teen posts heartbreaking message before she's swept away by Hurricane Harvey flood

Devy Saldivar. Photo / Facebook

Six members of a family have drowned in Houston after their van was swept away by currents in the Hurricane Harvey floodwaters in the deadliest single incident since the storm began.

Devy Saldivar wrote a heartbreaking message on Facebook as Tropical Storm Harvey bore down on their home.

"No sleep & anxiety, please let this pass sooner," 16-year-old wrote about 5:30 a.m. Sunday.

A few hours after her plea, her great-uncle, Sammy, tried to drive all of them to safety when violent floodwaters engulfed their van near the Greens Bayou, relatives told NBC News.

The driver - the children's great-uncle - was able to escape, but the van sank too quickly for the victims to be rescued, KHOU 11 reported.

Her brothers and sister Dominic, 14; Xavier, 8; and Daisy, 6, as well as their great-grandparents, Manuel, 83, and Belia, 81, all drowned.

The van ran into trouble van after it crossed a bridge and hit high floodwater on Green River Drive.

The survivor, who has not been identified, managed to grab onto a branch and told the children to climb out of the back door of the van, but they were unable to do so.

Instead, it sunk quickly - taking the family with it.

Witnesses to the incident said that although there were emergency crews in the area, it happened too fast for them to respond.

The bodies have not yet been recovered. Three family members confirmed the incident, but authorities have yet to release an official statement.

As of 3pm CT, the children's grandmother, Virginia Saldivar, was awaiting rescue.

"If anyone has a boat that can come rescue us on Talton St please come," she posted on Facebook. "'This is getting so scary with the water rising."

Adriana Saldivar replied: "We gave the helicopter people your address they will be looking at roofs and open space."

A GoFundMe account set up to help the family of the dead children was posted to Virginia Saldivar's page.

- NZ Herald and Daily Mail