The centers, in Taipei, Kaohsiung, Yilan County, and Nantou County, have a capacity of 300-400 people each but are now 80 percent full, with most occupants being Vietnamese, Taiwan News reported.

In March the National Immigration Agency unveiled an amnesty program for visa overstayers who turn themselves in. Around 800 Vietnamese reported and were sent to the detention centers, Taiwan's Central News Agency reported.

But the Immigration Act prohibits holding anyone for more than 100 days. Immigration authorities are therefore seeking assistance from the Taiwanese Ministry of Foreign Affairs and the Vietnamese government to send them home to Vietnam by special flights.

Taiwan said normal deportation is "impossible" since Vietnam has suspended all international flights.

In the last few months several special flights have been arranged to bring back over 5,000 Vietnamese from around the world stranded due to the Covid-19 outbreak and resultant closure of borders.

Taiwan is meanwhile planning to reduce the quarantine period from 14 to five days for people arriving from Vietnam due to the country’s "low-risk" Covid-19 status, according to the Central Epidemic Command Center.

Vietnam has had 332 cases so far, with only 12 people still in hospital and no deaths. Taiwan has had 443 confirmed cases and seven deaths.