Fresh cases of diphtheria have been found at the asylum seeker processing centre at Manston in Kent.
It comes after the UK Health Security Agency (UKHSA) confirmed an increase in instances of the highly contagious disease among asylum seekers arriving in the country.
A man held at Manston died in hospital on November 19 after crossing the Channel seven days earlier.
Although initial tests came back negative, a follow-up PCR test indicated "diphtheria may be the cause of the illness", Government officials said.
A post-mortem examination is being carried out to determine the cause of death.
The fresh cases were reported by GB News along with footage of a large dormitory where those being accommodated sleep close to each other.
A total of 161 migrants were intercepted by the UK authorities crossing the English Channel in 14 boats on Thursday December 1, with one boat arriving in the UK in an "uncontrolled landing", according to Ministry of Defence figures.
A Home Office spokesperson refused to provide a number of new cases of diphtheria at the Kent centre, saying it would not give a "running commentary" on cases.
He said: "It is untrue to suggest there is an outbreak on site. Migrants are arriving at Manston with diphtheria. We take both the welfare of those in our care and our wider public health responsibilities extremely seriously.
"We work closely with the NHS and UKHSA to support individuals affected by infection and limit transmission, as well as ensure information is shared in a timely way and that everyone leaving facilities such as Manston is given access to appropriate treatment.
"The Home Office provides 24/7 health facilities at Manston as well as having robust contingency plans to deal with health issues such as communicable diseases."
Immigration Minister Robert Jenrick said on Monday asylum seekers with symptoms of diphtheria would be put into isolation in a designated area while being treated.
Any asylum seekers who may have the infection but are already in hotels will be told to isolate in their rooms while they are treated.
Home Secretary Suella Braverman has faced criticism about overcrowding and outbreaks of disease at Manston.
The UKHSA said there had been an "increase" in cases of diphtheria reported among asylum seekers arriving in the UK, with 50 identified as of November 25, including children. The figure stood at 39 on November 10.
Mr Jenrick told the Commons on Monday the isolation centres would be "secure isolation hotels", such as those used during the coronavirus pandemic, and migrants would then be moved to other accommodation once they had made a full recovery.
The level of infectious diseases in migrant camps in northern France is also being assessed, he added.
Earlier in November, Mr Jenrick said all migrants were being offered a vaccine on arrival in the UK and he added that the acceptance rate was "increasing".
Ministers and health officials have insisted the risk of the public getting diphtheria is very low and infections are rare.
The illness - which affects the nose, throat and sometimes skin - can be fatal if not treated quickly, but antibiotics and other medicines are available.
Some public health experts have raised concerns about the spread of the disease as migrants were moved to hotels.