The London Fire Department is on the scene of an apartment fire at 654 King St.
Officials tweeted that they arrived at the scene shortly after 7 a.m.
Emergency crews have closed Marshall Street as they work to get the fire under control.
Officials say there were no injuries reported. There has been no word on damage estimate so far.
The London Fire Department is working with members of the London Police and Middlesex London Paramedics.
London fire investigators have now been called in to probe the scene for a cause and origin.
The London Fire Department says crews are being rotated out and overhaul operations are underway.