A man was arrested in three supermarkets in western London on suspicion of contaminating food with syringes, the council said.
The Hammersmith and Fulham council said police were called shortly before 8 pm after a man was reported screaming abuse to people on the street.
He allegedly visited three supermarkets on Fulham Palace Road, including Tesco, Waitrose and Sainsbury’s, and used numerous syringes to inject food.
The man was detained by police for attempting to cause public harm and anxiety.
The supermarket is closed and the crime scene is in place.
According to the council, the affected items are considered to be processed meats and microwave-compatible products.
It is currently unknown how many items are contaminated with what substances.
The Hammersmith and Fulham Council issued an “emergency alert” notice on its social media account on Wednesday night.
It states: “People are advised as a precautionary measure to dispose of food purchased tonight from these supermarkets.
“The H & F Council’s environmental health team is currently working with affected supermarket branches.”
The Metropolitan Police Department is being asked to comment.