Nine assembly line workers at the Mini car factory in Oxford have tested positive for coronavirus.
BMW, which owns the plant, said it is “monitoring the situation” and the site remains open following “detailed” talks with Public Health England.
Production at the factory in Cowley was halted in March because of the pandemic but resumed on 18 May.
BMW said it had made a “wide range of practical modifications”, which are being monitored daily.
It is understood that eight of the nine staff affected are from one section of the assembly line and were on the same shift. The other worker is also from the assembly line but from another section of it.
A BMW Group (UK) spokesman said: “Before restarting production we made a wide range of practical modifications and enhanced personal hygiene and cleaning routines, as well as giving clear instructions to everybody on site, in order to minimise the risk of transmission in the workplace as far as possible.
“These measures, which are fully in line with government health and safety guidance, are monitored on a daily basis in the best interests of our employees.”
All positive NHS coronavirus tests were returned in the last week and all staff are self-isolating.
Public Health England said anyone identified as a close contact of any positive case is being advised to self-isolate for 14 days even if they have no symptoms.
The plant in the city employs 4,500 people and produces 5,000 cars a week.
BMW took over the plant in 2001 but cars have been built on the site since 1913.
Last year a convoy of 60 Minis weaved through Oxford to mark the vehicle’s 60th anniversary.