People are being urged to throw food away that was purchased from three supermarkets in west London on Wednesday evening after a man is alleged to have injected foodstuffs with an unknown substance.
The man has been arrested by Metropolitan Police on suspicion of contaminating food with a syringe at Tesco Express, Little Waitrose and Sainsbury's Local, all on Fulham Palace Road.
Hammersmith & Fulham Council said officers were called just before 8pm after he was reported to be shouting abuse at people in the street.
Met Police later said in a statement the man was alleged to have "injected foodstuffs with a number of needles" at the Tesco Express at 168-188 Fulham Palace Road, the Little Waitrose at 201-207 Fulham Palace Road, and the Sainsbury's Local at 179-183 Fulham Palace Road.
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.
The affected items are believed to be processed meat and microwaveable products, according to the council.
It is currently unknown how many items have been contaminated, or with what substance.
Hammersmith and Fulham Council issued an "emergency alert" notice on its social media accounts on Wednesday evening.
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."
The Met Police said that investigations are on-going to establish if other businesses in the area are involved and that the Local Authority Environmental Health team have been informed and are working with the supermarket branches affected.