Dozens of foreigners have been put in quarantine for Middle East respiratory syndrome, but health authorities have yet to identify all of their nationalities, sources said Tuesday.

The Health and Welfare Ministry said that about 20 to 30 foreigners in Korea were ordered to be under home monitoring as they were suspected to have been exposed to MERS-confirmed patients.

As of Tuesday, more than 5,000 individuals in the country are being monitored at home for possible infection.

The exact number and nationality of those concerned has not been fully confirmed because the information of their home countries was not collected in the initial stages of the screening, according to the ministry.

“Once the MERS response team sends the list of those that they assume could be foreigners, we first identify based on names whether they are Korean nationals or not, and then proceed with the personal identification. So far, it may be uncertain, but there are believed to be around 20 to 30 expats under quarantine monitoring,” a Health Ministry official who is in charge of foreign affairs told The Korea Herald.

“The nationality identification is underway, but even if everything is confirmed, their nationalities will be kept confidential because of diplomatic issues,” she said, adding that some countries ask that the information not be released.

She stressed that the foreigners were being monitored by local health offices just like other Koreans.

Once the home monitoring is ordered, residents are required to stay at home for two weeks and receive a check-in call from the health authorities each day.

Health authorities said all those placed in quarantine, regardless of their nationality, are banned from traveling abroad by the Justice Ministry. The authorities need only the name, date of birth and address of those quarantined to ban the travel.

Monday, concerns were raised after two Japanese citizens, who were supposed to be in quarantine, were confirmed to have returned to their country earlier in the day. The ministry said they left the country before the home isolation measure was imposed. Both once visited Samsung Medical Center where over 70 cases of infection were reported, the ministry said.

While the two Japanese citizens tested negative in a preliminary MERS test, they remain under Japanese government monitoring, Japanese news outlets reported.

Last week, one Chinese person was found to have caught the virus while working at a medical facility in Dongtan, Gyeonggi Province.

As part of the efforts to contain the virus spreading to other countries, the Justice Ministry said it would allow the stay extension of those infected or under monitoring.

The ministry also urged foreign nationals in Korea to actively report any potential MERS symptoms, along with any possible contact with a patient. It said foreign residents can also receive emergency government subsidies allocated for MERS patients and those quarantined for possible infection, if they comply with the government instructions. The emergency subsidy ranges from 409,000 won ($366) to 1.41 million won for one-person to six-person households.

The MERS hotline ― 109 ― started to provide services in 19 different languages on Monday, including English, Chinese, Japanese, Spanish, French and Vietnamese.

Of more than 2,300 individuals in quarantine in the capital, no foreign nationals have been reported so far, Seoul City officials said.

By Lee Hyun-jeong (rene@heraldcorp.com)