It's the latest setback for the controversial barge the UK government hopes will provide an alternative to housing migrants in hotels.
Migrants have been temporarily removed from the controversial Bibby Stockholm barge after traces of Legionella bacteria were found in the water system on board.
As a result, everyone living on the barge in Dorset, in the south of England, is likely to be taken to alternative accommodation as a precautionary measure.
A UK Home Office spokesperson said the health and welfare those on board the vessel "is our utmost priority".
The Bibby Stockholm is one of a number of sites the UK government is trying to set up to provide an alternative to housing migrants in hotels.
The government is planning to house 500 men aged 18 to 65 on the barge who are awaiting the outcome of asylum applications. The Home Office says that 39 people have so far moved on board.
However, it has proven controversial, with protests from local people, politicians and pro-migrant groups before anyone even got on board.
The Home Office spokesperson added that samples from the water system had shown "levels of legionella bacteria which require further investigation."
"As a precautionary measure, all 39 asylum seekers who arrived on the vessel this week are being disembarked while further assessments are undertaken," he added. "No individuals on board have presented with symptoms of Legionnaires', and asylum seekers are being provided with appropriate advice and support."
"The samples taken relate only to the water system on the vessel itself and therefore carry no direct risk indication for the wider community of Portland nor do they relate to fresh water entering the vessel."
"Environmental samples from the water system on the Bibby Stockholm have shown levels of legionella bacteria which require further investigation," they said.
Legionella bacteria can cause a serious infection called Legionnaires' disease. If it's in water tanks and plumbing systems then it raises the danger that someone may breathe in infected water through something like taking a shower.