Four more workers at Samsung Electronics Co.'s mobile research lab have tested positive for the novel coronavirus, the company said Wednesday, stoking concerns of group transmissions at the facility.

The South Korean tech giant said an additional four virus cases were confirmed at its R5 lab in Suwon, south of Seoul, after it came out earlier this week that three workers were infected with the virus.

They all worked on the same floor with an employee who tested positive for COVID-19 on Sunday.

"The workers tested positive while they were ordered to stay at home after the first virus case," a Samsung official said. "Health authorities are investigating how they contracted the virus."

Samsung said some 300 employees took virus tests following the first case reported on Sunday, though most of them received negative results.

The world's largest smartphone maker shuttered the entire R5 building Monday, though it reopened later after disinfection. The floor where the virus-infected employees worked is scheduled to be closed through Wednesday.

Samsung said it has ordered employees who worked on the virus-hit floor to work from home for at least two weeks.

Samsung also reported a virus-infected worker at the R5 building on Nov. 18 but said that employee has been working on a different floor.

Meanwhile, South Korea reported 382 more COVID-19 cases, including 363 local infections, on Wednesday. (Yonhap)