Myanmar reported 23 cases of coronavirus infection on Friday among a group of people held in quarantine there after being deported from Thailand.
The health ministry said in a statement the group had tested positive while in a quarantine center in the southeastern Kayin state.
Thant Zin Aung, a lawmaker for Myanmar's Myawaddy township, which borders Thailand, said all 23 had been deported to Myanmar from Thailand on June 8. They had been in a Thai detention center close to the Malaysia border over visa violations, he said. At least some had earlier been detained in Malaysia.
Malaysian and Thai authorities have been detaining and deporting migrants from Myanmar in recent weeks as part of efforts to curb the spread of the coronavirus. Many are believed to be refugees from the Rohingya ethnic minority, hundreds of thousands of whom have fled a crackdown in Myanmar.
A Myanmar health ministry spokesman for the coronavirus response did not comment when contacted by Reuters.
The 23 cases were the most officially reported in a single day in Myanmar, which has recorded only 286 cases of the virus so far and six deaths. Testing has been limited.
Thailand has reported no local transmission of the coronavirus for almost a month, only imported cases. Taweesin Wisanuyothin, spokesman for the Thai government's COVID-19 Administration Center, told Reuters the public health ministry had carried out random tests on more than 500,000 people including migrant workers but did not find any infections.
"Myanmar authorities have to investigate from the patients who just returned what their travel history is and where they have been," he said.
Most curbs on movement within Myanmar have been lifted but on Monday authorities extended a ban on international flights until the end of June.