Residents in Seaford were told to stay indoors after reports of a noxious odour led some to complain of stinging eyes and nausea.
Emergency services advised people to keep doors and windows shut after several people contacted Sussex Police on Friday to say they smelt “burning plastic”.
The odour was first noticed in The Ridings area at about 6pm but failed to disperse, Sussex Police said.
East Sussex Fire and Rescue Service said on Saturday that they had been unable to ascertain the source of the odour.
The fire service advised people who have concerns about the odour to remain indoors, keeping doors and windows shut and report it to the fire service.
This incident comes nearly two months after scores of people were hospitalised when a chemical haze on the Sussex coast left holidaymakers with streaming eyes, sore throats and vomiting.
Emergency services warned people along the East Sussex coast to keep doors and windows closed after people were affected along the shoreline from Eastbourne to Birling Gap, near Beachy Head, although this advice was later withdrawn when the cloud dissipated.
Police said that the Seaford incident is not currently being linked to the chemical haze from August.