Four residents of a Palestinian refugee camp in Lebanon tested positive for the coronavirus on Thursday, bringing total cases there to five.
Residents of the Wavel camp in the eastern Bekaa Valley were tested after a member of their household, a Palestinian woman from Syria, was admitted to the Rafik Hariri hospital in Beirut this week after showing Covid-19 symptoms.
Contact tracing and investigation by the health ministry of the woman showed four members of her household were affected, Firas Abiad, the hospital's manager, said on Twitter.
"All contacts are in quarantine and under observation," Mr Abiad said.
Lebanon has officially announced 688 infections including 22 deaths from Covid-19.
Medical experts visited the Wavel camp on Wednesday to carry out tests on the relatives, people with whom the woman has come into contact and 50 others randomly selected from the camp, Lebanon's official National News Agency reported.
All other tests have returned negative, Mr Abiad said.
There have been no reports of coronavirus in other Palestinian camps in Lebanon.
In co-ordination with Lebanese police, Palestinian factions in charge of security have imposed a lockdown on Wavel, stopping anyone entering or leaving, the NNA reported.
More than 2,000 people live in Wavel, say statistics released by Lebanon after a 2017 census.
But the UN agency for Palestinian refugees says the population of the camp is much higher.
Aid groups have warned that hundreds of thousands of Palestinian and Syrian refugees in Lebanon's overcrowded camps are the most vulnerable.
They say isolating patients in the camps, where sanitation is poor, would be a major challenge.
More than 174,000 Palestinians live in Lebanon, official figures show, with most in camps ruled by Palestinian factions beyond the reach of Lebanese security forces.
But unofficial estimates say the Palestinians, whose families fled the creation of Israel in 1948, could number as many as 500,000.
Lebanon says it also hosts 1.5 million Syrians since civil war broke out in the neighbouring country nine years ago, nearly one million of whom are registered with the UN as refugees.
One other Palestinian, who does not live in a camp, and three Syrians had tested positive in Lebanon for Covid-19.