Fire crews may have to wait days to discover whether a large fire at a building in Manchester city centre claimed any lives.
The fire spread to an office block on the opposite side of the road
There have been reports that homeless people were sleeping rough in the five-storey block in Dale Street.
The blaze spread to a second block on the other side of the street.
Greater Manchester Fire and Rescue Service said it would be unable to get crews inside until it was deemed safe to sift through the burnt out shell.
Rhys Griffith, chief fire officer at the scene, said: "Until we can get in, we won't be able to confirm whether anyone was inside.
"It is likely to take days rather than hours before we find out."
More than 120 firefighters were called to tackle the fires in the city's Northern Quarter when the alarm was raised early on Monday morning.
An investigation is under way into the cause of the fire and how it spread to the second block on the opposite side of the road.
Supt David Hull, of Greater Manchester Police, said he could not rule out the possibility that there were casualties inside the first building.
He said: "We have received a number of reports that there may have been homeless people sleeping rough in the building.
"We are currently following up those reports.
"There remains the possibility that there are casualties inside, but we won't know until it is safe to go in.
"If anyone was inside, then this would probably be a body recovery situation rather than a rescue."
About 50 firefighters remain at the site with structural engineers and gas experts.
Newton Street is now open to both cars and pedestrians in both directions.
Back Piccadilly is also open from Newton Street to Spear Street and Lever Street is open to pedestrians only from Piccadilly to Hilton Street.
Dale Street remains closed from Lever Street to Newton Street and Little Lever Street is closed from Back Piccadilly to Hilton Street.