Story highlights "Hundreds" of people were affected by unexplained haze, according to police

No confirmation yet on the type of gas or how it had arrived in the UK

(CNN) Around 150 people have been treated at hospital after being caught in a mysterious "chemical haze" that blanketed the UK's East Sussex coastline Sunday afternoon.

Residents exposed to the cloud reported eye and throat irritations, a spokesperson for the National Health Service told CNN.

In a statement, police warned "hundreds more" people across the region could have been affected.

There are no indications yet as to what caused the haze, though East Sussex Fire and Rescue Service have termed it a "chemical incident."

Cloud moving towards Eastbourne Bexhill area please be aware pic.twitter.com/d5ug7KckuF — C/Insp Bruce Mathews (@CIBruceMathews) August 27, 2017

Authorities said the problems began when the "unknown haze" covered the area after possibly coming in off the sea at about 5 p.m. local time.