Several residents of a downtown Atlanta high-rise building were forced to evacuate after a fire broke out Wednesday evening, officials said.

Atlanta fire Assistant Chief Gary Robb told Channel 2 Action News that firefighters had just wrapped up a separate call and were driving through the area around 6:15 p.m. when they noticed the Landmark Condominium on Piedmont Avenue was ablaze. At that point, no one had been able to call 911, the news station reported.

The fire began on the first floor and extended to a second-floor condo, the fire department said. Smoke also infiltrated the third and fourth floors.

About 50 residents were evacuated and sheltered in a MARTA bus as crews worked to extinguish the flames. Those above the fourth floor were asked to shelter in place.

Six people were treated for smoke inhalation, with one of them requiring transportation to a hospital, officials stated.

The Landmark Condominium is a 21-floor high-rise located less than a mile east of Centennial Olympic Park. The cause of the fire remains under investigation.

— Please return to The Atlanta Journal-Constitution for updates.