What caused a blaze to gut a Red Top business on U.S. Highway 17 remained a mystery Friday as the St. Andrews Fire Department continued its investigation into the fire.

Fran Roberts, the owner and second generation partner of Roberts & Sons Signs, on Friday surveyed the damage to his family’s business after flames ripped through the establishment the night before.

The business was founded in 1957, Roberts said. The family plans to rebuild, once the business is cleared to do so.

Flames ignited at Roberts & Sons Signs at 3915 Savannah Highway about 9 p.m. Thursday.

Flames had already breached through the business’ roof when first responders arrived at the scene about five minutes after receiving the call.

The St. Andrews Fire Department was assisted by the Charleston Fire Department and the St. Johns Fire Department, as well as Charleston County EMS, the Charleston Police Department, and the Charleston County Sheriff’s Office, St. Andrews Fire Marshal Nathan Murtaugh said in a news release Friday.

Firefighters battled the flames from the exterior of the business, Murtaugh said. Crews established a water supply that subsequently blocked traffic in both directions on Savannah Highway, he said.

Firefighters managed to put out the fire in about an hour. About 30 percent of the building was damaged, Murtaugh said.

Authorities are uncertain of the fire’s cause. Murtaugh said more information would be released about the incident pending the investigation.

One firefighter was taken to a hospital for heat-related illness, Murtaugh said. That firefighter was treated and released.