Four floors of a downtown Saskatoon building were evacuated Thursday after a report of a suspicious package.

Emergency crews, including firefighters and hazmat teams, were called just before noon to the River Centre building, at the corner of 19th Street East and Second Avenue South. Police confirmed a package containing an unknown substance prompted the emergency response.

Hazmat teams evacuated the building’s second to fifth floors after discovering the envelope and worked to decontaminate two people on the fifth floor who contacted the package. The move was precautionary, the fire department said in a media release.

The content of the package was eventually found to be aluminum hydroxide, which is often used as an antacid.

“It’s the uncertainty, the unknown of actually what the product is, so when we respond to these types of incidents, we have to respond with the idea it could be a worst case scenario,” Assistant Fire Chief Wayne Rodger said on scene.

“It could actually be a dangerous product that could impact the health of the occupants that are in close proximity.”

Aluminum hydroxide is not dangerous, not harmful if touched and not used as an explosive, Rodger said. The two people who contacted the envelope were unharmed.

Saskatoon fire crews and hazmat teams have since left the block and Saskatoon police are taking over the scene, the fire department said.