A number of mystery fires in rubbish and waste bins near city centre business premises and living accommodation has sparked a police warning to traders and extra patrols.
Officers say so far there is insufficient evidence to show whether all the fires are deliberate or linked, but the worst one adjacent to a major hotel is believed to be arson.
The City Neighbourhood Policing Team (NPT) is urging businesses in Leeds city centre to guard against fire attacks in their bin storage areas.
The most serious incident was behind the Hotel Metropole on King Street shortly before 5am last Monday where rubbish was piled up in an alleyway before being set alight, said a spokesman.
"The incident is being treated as suspicious and detectives from City and Holbeck CID are following enquiries including examining local CCTV footage," he said.
There have been a number of other incidents where rubbish or bins have been set alight behind premises and in alleyways in the city since then, he added.
Rubbish from bins on Albion Place was set alight late on Wednesday evening and another incident was reported by premises on Lands Lane on Thursday morning.
"There is no information to suggest any of the incidents are linked, and NPT officers are paying extra attention to the areas affected," said the spokesman.
Sgt Martyn Mynard, said: "It is unclear whether the fires are malicious or accidental, but there is still a serious safety risk posed by them and it's important that we work together to prevent further incidents.
"We'll be putting additional patrols in the areas each evening and for the time being I urge businesses to think about how they store rubbish and waste outside their premises."
One woman was in her second floor flat in Albion Place above the Body Shop and Costa Coffee premises when she smelled smoke at about 11.30pm on Wednesday.
She said: "We were effectively trapped in the building. There were lots of plastic bags and two wheelie bins on fire. It was very frightening."
If anyone see anything suspicious contact the City Neighbourhood Policing Team via 0845 6060606.