Finland's Rauma Marine Constructions (RMC) has been closed following a mass outbreak of coronavirus.

Authorities said a total of 240 shipyard workers have tested positive for Covid-19 and nearly 800 are in quarantine. The shipyard was shut on 19 February.

Hannu Nordqvist, RMC's chief doctor, said about 80% of the workers are foreign and that efforts to minimise the spread of the virus were hampered by language barriers and cultural differences — one being that workers often live communally and commute to work together.

"Their living areas were not divided, so there is the possibility that infected individuals exposed and infected others there," Nordqvist said.

The doctor said many workers did not initially realise that quarantine instructions were legally binding.

However, information has since been updated in native languages.

RMC chief executive Jyrki Heinimaa said the company is carefully investigating the situation in cooperation with local health authorities.

He added that any decisions on reopening the yard would be made together with those authorities.

No workers have required hospital treatment yet, but all of the affected employees will be required to undergo a coronavirus test before being permitted back on the job.

"Going forward, the scheduling of employees' working shifts and breaks will be staggered to minimise contacts at the dock area," RMC said.

The shipyard is building two ropaxes: one LNG-powered vessel for Tallink, due in 2022, and the other for Kvarken Link, which is set for handover this year.

The facility was formerly named STX Finland, but this plant closed down in 2013.

The yard was then bought by the city of Rauma in 2014. It has since completed a ferry for Molslinjen.