VANCOUVER (NEWS1130) – The return home for people living in the Electra could be delayed again, by yet another mystery deep below the building.

The chemical smell has evaporated, at least at street-level. Vancouver fire crews are still on stand-by, and the focus of the city investigation has shifted to a sealed underground vault.

The Vancouver Sun reports it was punctured by the contractor on-site, who then filled it with expanding foam – that created enough heat to spark an underground fire.

There are now worries the vault contained PCBs used by the hydro substation next door. Vancouver Coastal Health still isn’t expressing an official medical concern.

People were ordered from the building on Friday.  Streets in the area remain closed.