After a lengthy investigation, police and fire department officials have concluded that a major fire was deliberately set in Ottawa's Chinatown neighbourhood last August.

The fire destroyed several buildings at Somerset and Booth streets. It left 33 people homeless, and caused more than $2 million in damage.

The police arson section and the fire marshal's office worked together on the investigation and won't say what led them to decide that the fire was the work of an arsonist.

More than 60 firefighters battled the flames and dense smoke billowing out of the four-alarm blaze Aug. 16, in what fire department platoon chief Jim Corrigan called one of the biggest fires of the year.

Ottawa police admitted at the time the fire marshal would have a tough time figuring out what caused the fire.

Paramedics treated one person and three cats for minor respiratory problems at the scene, the Ottawa Paramedic Service said in a news release at the time. One firefighter was sent to hospital for a knee injury.

Two years before, right across the street, a fire at the Mekong Grocery killed five members of one family.