A long-burning blaze in downtown St. Catharines has left parts of the core shut down as fire crews continue their work.

A fire broke out late Friday night at 17 Queen Street, the former St. Catharines Standard building, and burned for nearly 18 hours before firefighters brought it under control early Saturday evening. The upper floor and other sections of the structure were heavily damaged, with part of the roof collapsing. Crews used an excavator to access hidden hot spots and fully extinguish remaining fire.

Queen Street and William Street remained closed Sunday, and the city advised residents to stay clear of the area. William Street is expected to stay closed through Monday morning to maintain safety while crews continue operations.

Because the building is too unstable, officials have ruled the cause undetermined and the Fire Marshal will not conduct an investigation. No injuries have been reported.