The fight broke out on Saturday evening (credit: Google Maps)
The incident broke out at the Impulse Leisure Centre in Blackshots Lane, at around 9.40pm on Saturday.
Four men and a woman who were assaulted have been identified.
Enquiries are ongoing.
Anyone with information or video footage is asked to call police on 101, quoting the crime reference number 42/36784/20.
Alternatively, contact Crimestoppers anonymously on 0800 555 111.
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Tags: Grays, Thurrock