The Shizuoka prefectural government issued a virus emergency alert Tuesday, a day after three cases of infection with a new coronavirus variant were confirmed in the central Japan prefecture.

Shizuoka Gov. Heita Kawakatsu announced the alert at a press conference, saying while the prefectural government still lacked information on the spread of the new variant, "It is necessary to take more thorough infection prevention measures and further strengthen measures for medical care provision."

Shizuoka Gov. Heita Kawakatsu gives a press conference at the prefectural government office in the central Japanese prefecture on Jan. 19, 2021. (Kyodo)

The cases were the first confirmation in Japan of people infected with the new variant, the transmission routes of which could not be traced, according to the health ministry.

Japan's health minister said the same day that the government will find out whether the coronavirus variant, initially detected in Britain, is spreading in the country by collecting samples from infected people in the prefecture.

"We need to firmly examine the situation," Health, Labor and Welfare Minister Norihisa Tamura told a press conference, while adding there was no evidence at the moment that the variant was spreading in Japan.

On Monday, three people in their 20s to 60s were confirmed to be infected with the variant in the prefecture. None of them had traveled to Britain or had prior contact with people who have recently been to the country.

After the variant was detected in Britain, Japan's National Institute of Infectious Diseases began undertaking genomic analysis of samples from people infected with the novel coronavirus to assess the potential spread of the variant.

The infections in Shizuoka Prefecture were confirmed through this method.