Thirty deaths related to Helene have been confirmed in Buncombe County, the sheriff said Sunday evening at a news conference.

Search efforts were still in progress, Sheriff Quentin Miller said, adding that they may include recovery operations.

“We are grieving tremendous losses today,” Miller said.

That casualty toll was a sharp increase from the morning, when 10 confirmed deaths in Buncombe County were announced. In the afternoon, Gov. Roy Cooper put the toll at 11 but did not say whether his figure included deaths in Buncombe County.

Related: Two deputies died in Helene flooding in western North Carolina

Much of western North Carolina remains partly cut off from the rest of the state after devastating flooding brought on by Helene earlier this week, and Buncombe County is still in a state of emergency.

Authorities said they were working Sunday to set up distribution sites for food and water but had been hindered by lack of cellphone reception. All roads in western North Carolina should be considered closed and non-emergency travel is prohibited, according to the state road condition website DriveNC.

A tanker carrying water arrived in Black Mountain Sunday afternoon; residents were asked to bring their own containers.

The risk of landslides caused by heavy rains persisted Sunday, County Manager Avril Pinder said at the news conference.

“We have areas in Fairview, Black Mountain, Swannanoa and Barnardsville where the devastation is unthinkable,” Pinder said.

She urged residents who felt unsafe to go to a designated shelter but noted that the WNC Agricultural Center was at capacity and directed evacuees to go to the A-B Tech Conference Center.

Related: Recovering from Helene: Shelters, resources and closings

In other counties in the mountain region, flooding related to Helene has caused the deaths of two deputies.

Macon County Deputy Jim Lau was last seen Friday when his truck went underwater in a river, the county sheriff's office stated. His body was recovered Saturday morning.

The North Carolina Sheriffs’ Association said in a Facebook post that a Madison County Sheriff’s Office deputy was killed in floodwaters.