Myanmar police arrested nearly 100 ethnic Rohingya on Wednesday after raiding a house in the commercial capital of Yangon, police and local media said.
Photos published by the local Tomorrow News Journal showed several barefoot men and dozens of women in colourful head scarves sitting on the ground in a courtyard.
Myanmar frequently detains Rohingya, members of a Muslim minority, on grounds of "illegal travel" for attempting to leave their native western Rakhine state.
Tin Maung Lwin, a police captain from Shwe Pyi Thar township, where the group was found, confirmed the arrests but declined to give further details.
"The investigation is still ongoing," he said, adding that either 98 or 99 people had been arrested. He said they would be sent to a quarantine centre to prevent the spread of Covid-19.
Some 600,000 Rohingya live in Myanmar under what Amnesty International has called "apartheid conditions", mostly confined to camps and villages and unable to travel freely or access healthcare or education.
The vast majority lack citizenship and are considered illegal immigrants from neighbouring Bangladesh, despite many tracing their ancestry in the country back hundreds of years.
"It is outrageous that Myanmar authorities continue their policy of arresting Rohingya for merely travelling in their own country," said John Quinley, senior human rights specialist at Fortify Rights. "The group arrested in Yangon should be immediately and unconditionally released."
A government spokesman did not immediately respond to a request for comment.
More than 730,000 fled to Bangladesh in 2017 to escape a military-led crackdown that UN investigators have said was carried out with "genocidal intent" and included mass killings and rapes.
Myanmar denies accusations of genocide and says the army was fighting a legitimate counter-insurgency campaign against militants who attacked security posts.
In recent years, hundreds of Rohingya have been imprisoned in jails and youth detention centres across the country after being caught leaving Rakhine, many seeking to flee to Thailand and Malaysia. Others have been returned to camps.
The government says it is working on a national strategy to close camps and that Rohingya would not face movement restrictions if they accepted a so-called national verification card, an identity document many reject because they say it labels them foreigners.