A man has been arrested on suspicion of contaminating food with a syringe at three supermarkets in west London, a council has said.
Hammersmith & Fulham Council said officers were called at just before 8pm after a man was reported to be shouting abuse at people in the street.
He is alleged to have visited three supermarkets, including Tesco, Waitrose and Sainsbury's, in Fulham Palace Road, and injected foodstuffs using a number of syringes.
The man has been taken into police custody accused of trying to cause public harm or anxiety.
The supermarkets have been closed and crime scenes are in place.
Hammersmith and Fulham Council issued an “emergency alert” notice on its social media accounts on Wednesday evening.
“The food items affected are believed to be processed meat and microwaveable products,” it said.
“It is currently unknown how many items have been contaminated, or with what substance.”
It said: "Members of the public are advised as a precaution to dispose of any food items bought from these supermarkets this evening.
"H&F Council's Environmental Health team are now working with the supermarket branches affected."