Twenty people were displaced after a fire damaged a North Charleston apartment building early Friday morning, authorities said. 

A smoke alarm alerted a sleeping resident at 4020 O'Hear Ave., near St. Johns Avenue, shortly before 3 a.m. The resident and others helped people evacuate before firefighters arrived. 

Flames spread from the second floor to the attic and the roof before the fire was extinguished, North Charleston officials said. 

The American Red Cross opened a reception center for displaced residents in Park Circle. Those affected by the blaze were encouraged Friday to visit the Park Circle Recreation Center, 4800 Park Circle, for possible lodging and financial assistance. 

Authorities continue to investigate what caused the blaze. 

The Charleston and St. Andrews fire departments assisted the North Charleston Fire Department. 

Reach Angie Jackson at 843-937-5705. Follow her on Twitter at @angiejackson23

Angie Jackson covers crime and breaking news for The Post and Courier. She previously covered the same beat for the Grand Rapids Press and MLive.com in Michigan. When she’s not reporting, Angie enjoys teaching yoga and exploring the outdoors.