An intense odour led to the evacuation of several homes in an east Hamilton neighbourhood Thursday evening.

Emergency crews were called around 7:30 p.m. after a resident smelled unusual odours coming from the basement of a home at 103 Barnesdale Ave. North.

Hamilton firefighters detected explosive levels of an unidentified substance and evacuated several homes in the surrounding area.

The emergency call was upgraded and the Hamilton Fire Department’s Hazardous Response Unit was called in to assist.

Hazmat crews discovered the explosive levels were ever more dangerous than original thought and the evacuation area was extended. An HSR bus was brought in to Tim Horton’s Field for the residents.

Investigators determined the odour was caused by a leak in propane tanks that were being to fuel a hot water heater in the basement of the home.

They believe the connection became loose and filled the home with such a dangerous level of gas that a spark could have ignited an explosion.

The home was ventilated and after several hours, the evacuees were allowed back into their homes.