Police say there have been 50 incidents of plastic bottles containing an unknown yellow fluid turning up on residents' properties across the region,
Police have been investigating from mid May to earlier this month after the bottles turned up in Niagara on the Lake, Grimsby, Niagara Falls, St. Catharines, Thorold, Pelham and Welland.
People are waking up to find the plastic bottles on their property, sometimes in the backyard.
Several of the bottles have been forensically examined by detectives from the NRPS Forensic Service Unit.
Police say the fluid in not volatile but are advising people to limit their contact with bottles.
Police say this may be a vetting technique by criminals to determine whether a homeowner is present.
Generally, the bottles are appearing with no associated damage or theft.