Industry sources said it would take weeks to clean all the pipes on the barge and then carry out new Legionella checks.
The first batch of water tests took 13 days, from sampling on July 25 until the results were reported to Landry & Kling, the contractor, on Monday of this week, revealing that Legionella had been found.
Legionella, which is commonly found in water, can cause a serious type of pneumonia known as Legionnaires’ disease, which is fatal in 10 percent of cases.
The Home Office said no migrants had fallen ill or developed Legionnaires’ disease. The asylum seekers were evacuated at 7 pm on Friday.
Legionella can cause serious illness in people over the age of 50, smokers, and people with underlying health conditions. Bacteria multiply when water temperatures are between 25°C and 50°C or if there is little or no flow to a water system.
Ministers intend the Bibby Stockholm to eventually house 500 migrants, but longer-than-expected repairs, bad weather and security checks had already delayed the first arrivals by a month.
It is one of three mass accommodation sites aimed at reducing the £6 million a day cost of housing 51,000 migrants in hotels. The other two are former RAF bases.