Police are interviewing witnesses after a suspicious package delivery prompted the evacuation of four floors in a downtown Saskatoon office building Thursday.

Emergency crews, including firefighters and a hazmat team, were called just before noon to the River Centre building, at the corner of 19th Street East and Second Avenue South. Police had received a report a suspicious package was delivered to the building.

The hazmat team evacuated the second to fifth floors after discovering the suspicious package. Crews decontaminated two people on the fifth floor who came in contact with the package.

The envelope was later confirmed to contain aluminum hydroxide, a non-hazardous chemical often used as an antacid, according to the fire department. The two who contacted the envelope were unharmed.

Police said Friday a detective has been assigned to the file and is interviewing witnesses.

Anyone with information is asked to contact police at 306-975-8300 or Crime Stoppers at 1-800-222-8477.