British police said they had arrested a man on Thursday after processed meats and microwave products were injected into three supermarkets in west London with various needles.
Little Waitrose, Sainsbury’s Local, and Tesco Express stores closed following the incident on Wednesday night.
Police were called after reports that the man had yelled insults at people, entered Fulham Palace Road shops, and injected food products.
“It is currently unknown how many items have been contaminated or with what,” the Metropolitan Police said in a statement. “Investigations are underway to establish whether other companies in the area are involved in the incident.”
People who bought food at supermarkets on Wednesday night were advised to throw it out. The man is being questioned on suspicion of contamination of goods to cause public harm.