Hamilton Mayor Andrea Horwath is calling for an investigation after city staff discovered a pipe has been dumping sewage into the local harbour undetected for 26 years.

Horwath says she has asked the city auditor to be brought in after a preliminary investigation of the pipe leak uncovered Tuesday morning suggests a contractor put it there in 1996.

The city says the combined sewer pipe services about 50 properties, which have been flushing directly into the Hamilton Harbour.

It says city staff were doing separate maintenance work on Tuesday when they found the hole in a stretch of pipe near Burlington Street and Wentworth Street North.

In a statement, the city says it believes a contractor made the hole under the impression that "all pipes were storm sewers" designed to connect to the culverts spilling into the harbour.

Horwath says she's been assured the risk to human health is "very low," but she raised concerns about the spill's environmental impacts. The city says once its assessment is finished it will publicly report how much sewage the pipe has dumped.

This report by The Canadian Press was first published Nov. 23, 2022.