Six people are dead and two are unaccounted for in the wake of heavy rains and devastating flash flooding in West Virginia, according to Gov. Patrick Morrisey.

“West Virginia has been hit very, very hard,” Morrisey said Monday.

A state of emergency is in effect and the West Virginia National Guard and Federal Emergency Management Agency officials are on the ground in Marion County, he said.

Flash flooding hit the city of Wheeling and the towns of Triadelphia and Valley Grove. Roughly 3 to 4 inches of rain fell in the area in a short period of time, prompting significant flash flooding along US 40 (National Road), Middle Wheeling Creek, Little Wheeling Creek and various runs and streams through Ohio County.

On Sunday, a residential building in the city of Fairmont, in Marion County, partially collapsed, prompting the emergency declaration, according to the governor.

Footage from the scene showed water rushing out of the severely damaged structure as emergency crews responded to the scene.

Displaced residents are now being housed at Fairmont State University, officials said.

The cause of the collapse has not been determined, the governor said Monday.

Officials said they are monitoring the situation as more rain is in the forecast over the next few days.

ABC News’ Darren Reynolds and Victoria Arancio contributed to this report.