Panicked residents evacuated the Barrington Plaza building in the 11700 block of West Wilshire Boulevard, gathering on the sidewalk outside as two fire trucks responded to the scene shortly before 9 p.m.
But no flames were apparent from the outside and the firefighters did not appear to be putting their equipment into use.
After it became apparent there were no visible flames, most residents returned to their units.
"It's like PTSD all over again," said building resident Ania Duncan. "This is literally one week from the first one. Are you kidding me?"
Residents say they were told someone had thrown a lit cigarette down a trash chute, setting off the alarm.
During the blaze on Jan. 29, firefighters had to evacuate people out the windows of the seventh floor with the help of ladders.
The burn marks are still visible on the exterior of the building.
Fire department officials noted at the time that the building is not equipped with fire sprinklers, one of 55 high-rises in Los Angeles that are not required to have them because they were built before 1974. Residents say it is time for the building to go ahead and install sprinklers.
Los Angeles City Councilman Mike Bonin is expected to introduce a measure requiring all high-rises to have sprinklers, no matter when they were built.
The same building was the site of another fire in October of 2013. Several people sued and the case was settled. A jury found the building's company was negligent then and responsible for injuries.