By CTV News Ottawa, November 10, 2016

Three workers were trapped in Ottawa's light rail transit tunnel near Waller Street and Laurier Avenue on Thursday after some concrete came loose and fell.

The three workers were in a 'safe zone' about 200 metres from the tunnel's entrance for about an hour. One suffered minor injuries and was taken to hospital; the others were unharmed.

While police initially called the incident a "tunnel collapse," Mayor Jim Watson later said at the scene that it was not a tunnel collapse; rather, workers were spraying concrete in a part of the tunnel and some rebar came loose and fell down.

http://ottawa.ctvnews.ca/incident-in-lrt-tunnel-not-a-collapse-city-insists-1.3155090