London fire crews were called to the scene of a fire on Dundas Street between McCormick Boulevard and Ashland Avenue on Tuesday afternoon.
Flames could be seen shooting from the roof of the old McCormick/Beta Brands cookie factory in the city's east end around 3:30 p.m.
Officials say when they arrived they found the fire in a wooden rooftop-access structure.
No one was injured, but firefighters had to take extreme caution due to the "questionable structural integrity" of the roof.
Dundas Street was completely closed for part of the afternoon, but by shortly after 4 p.m. all lanes had re-opened except for one westbound lane.
An investigatoin into the cause of the fire continues and there's no word on the extent of the damage.
The building has been vacant for years but there have been concerns with people using the structure for shelter.
Officials say they don't believe anyone was in the building when they arrived, but the fire had to start somewhere.
Fire crews work at the scene of a fire at the old McCormick/Beta Brands factory in east London, Ont. on Tuesday, Nov. 20, 2018. (Bryan Bicknell / CTV London)
