NINE new cases of COVID-19 reported in Bunbury on Wednesday, all related to the Kemerton Lithium Hydroxide Processing Plant.
As announced by Premier Mark McGowan, the nine new cases overnight bring the Bunbury cluster up to 16.
Treendale Farm Hotel has been listed an exposure site.
Anyone who attended the venue on Thursday, January 20 from 5pm to 6.30pm is advised to get tested immediately and isolate until they receive a negative result.
Mr McGowan confirmed that the virus had effected one contractor and one work site at the 90 hectare site in Kemerton.
"The area affected has been shut down and any close contacts in the work unit have been requested to get tested and isolated," he said.
"Since the first case was identified on Monday, there have been 99 close or casual contacts, with 73 returning negative results.
"The Department of Health is now working with the company to test and quarantine those affected."
According to Australian Manufacturing Workers' Union state secretary Steve McCartney, at least five workers at the Kemerton plant had been affected.
Despite Mr McGowan's comments, the union said the site's 600-strong workforce had been left in the dark about how the outbreak would be managed.
"Workers are fearful that they might contract the virus and take it home to their families," Mr McCartney said.
"They are being driven to site on crowded buses from accommodation, there has been no visible increase in cleaning and no instigation of split shifts or staggered breaks.
"Some contractors are telling their employees some information, and others have been completely mum. They all need to work with unions onsite and health and safety representatives to get this right."
An Albemarle spokesman declined to reveal the number of cases but said all workers at Kemerton were vaccinated and the site was adhering to WA Health protocols.
"Since the recent confirmation of positive COVID-19 cases at the Kemerton site, the infected persons have been isolated, as well as close contacts," he said.
"Close contacts are being tested in line with WA Health protocols. The site is working with WA Health COVID-19 contact tracing.
"The wellbeing and safety of our workforce and communities continues to be our priority."
The Bunbury cluster brings the state total for January 26 to 24 new cases.
WA Health advises anyone who is experiencing symptoms of COVID-19 to get tested.
The Bunbury COVID-19 testing clinic will be open until 6pm tonight.
Australian Associated Press