It is understood the restriction came into effect when the workers attempted to return to their workplace on Monday, February 24.
One concerned employee said: "We're not being told anything other than they've been told not to come in for 14 days.
"It's really worrying as we still don't know much about the disease. Everyone is taking measures like washing their hands regularly very seriously."
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A memo sent to Vauxhall staff last Wednesday stated that owner Group PSA is restricting access to visitors from countries with active Coronavirus circulation zones - currently mainland China, Hong Kong, Macao, Singapore, South Korea, Iran and Italy.
It stated: "Anyone arriving from one of these countries, for example from Italy, or who has stayed there in the last 14 days, is requested not to enter PSA sites."
A PSA spokesman said: “Groupe PSA has been working closely with their chief medical officer and first issued guidance on preventative measures in relation to the Coronavirus on February 4.
"Information covered what we have implemented to protect our workforce and reduce the risk of the virus spreading.
"Across Groupe PSA sites, any person coming from China, PSA employee or not, is subject to a 14-day access restriction to Group premises when arriving from the epidemic zone [all of China]. All external visitors arriving at our premises are also asked to complete a short questionnaire in application of this access restriction.
"A second communication was shared with employees on Wednesday, February 26, detailing further measures Groupe PSA was taking across all sites.
"We will continue to keep the situation under review and continue to share information with employees as appropriate.”