A dumped settee caught fire in a stairwell at a block of flats, blocking the fire exit.
Firefighters who tackled the blaze at the flats in Rutland Street, Melton, on Thursday night told residents to stay inside while they dealt with the fire.
Firefighters were called to the flats, near Morrisons supermarket, at about 5.25pm.
Initial reports said a flat was on fire, trapping four people and a dog, but firefighters found the fire was confined to the bottom of an internal staircase.
Incident commander Bill Smith, of Melton fire station, said there were five people and two dogs in four of the flats at the time of the blaze.
He said: "At this stage, we don't know how the settee was ignited. The fire caused smoke- logging to two floors of flats, which worried the residents. We put the fire out and told them to stay inside."
A woman who inhaled a small amount of smoke was checked over by paramedics.
Mr Smith said: "It's very dangerous to discard any combustible materials at a fire exit. If it ignites, people can't escape.
"We also need to make sure people have smoke detectors fitted and working and that they test them regularly."
Four firefighters wearing breathing equipment dealt with the fire and ventilated smoke from all the floors of the flats.
An investigation is under way into the cause of the fire.