People in a coastal town have been advised to stay in and keep doors and windows shut after reports of a noxious odour.
The emergency services issued the warning as people in Seaford, East Sussex, complained of stinging eyes and feeling sick on Friday evening.
One of several people to contact Sussex Police described the smell as being “like burning plastic”.
The force said the odour was first noticed in The Ridings area at around 6pm but failed to disperse.
Police are working with other agencies, including the coastguard, East Sussex Fire and Rescue Service and Lewes Council, to try to determine the cause of the smell.
In August, a toxic “haze” caused discomfort to people in the Birling Gap area, but police said the Seaford incident was not currently being linked to it.
Visitors to Birling Gap and other beaches in Sussex suffered sore eyes and breathing problems after a mystery gas was blown ashore from the English Channel on August 27.
It is believed the most likely source of the fumes was a ship illegally flushing its tanks with chemicals.