Police in Cambridge are investigating a fourth pharmacy robbery in the span of a month.

Waterloo Regional Police were called to the Shoppers Drug Mart at 1500 King Street East in Cambridge Sunday afternoon. Police say the suspect made off with an unknown amount of pain killers.

Prescription pills were stolen from the same store on the afternoon of Dec. 14.

Drugs were also stolen from the Preston Medical Pharmacy on Dec. 24, and on Jan. 6 prescription painkillers and cash were stolen from the Shoppers Drug Mart on Holiday Inn Drive.

Police believe the same man may be responsible for all four robberies.

Anyone with any information is asked to call police or Crime Stoppers.