A woman being held at Yarl's Wood immigration removal centre has tested positive for coronavirus, prompting calls for detainees to be released.
The Home Office confirmed the diagnosis on Sunday and said the woman had been placed in isolation at the Bedfordshire facility after showing symptoms.
No other staff or detainees have tested positive for Covid-19, the Home Office added.
The charity Women For Refugee Women said many of the detainees inside the facility had underlying health conditions, which could put them more at risk if they are infected.
The charity's director, Natasha Walter said:
Yarl's Wood, which is located near Milton Ernest, north of Bedford, houses women and adult family groups awaiting immigration clearance.
One woman, who has been in the centre for more than a fortnight, said: "Now they are taking precautions, but they were taking no precautions until yesterday. "So right now everyone is panicking. We know there is a pandemic going on and here we are not being given the means to protect ourselves."
Detainees arriving at immigration removal centres are medically assessed by a nurse within two hours of their arrival and a doctor within 24 hours, the Home Office said.
Hand washing facilities are available at all centres, the Home Office said, adding that it was working with suppliers to ensure there is adequate supply of soap and cleaning materials.
Bella Sankey, director of Detention Action, which supports people held in immigration centres, said:
In a statement, Ms Sankey said she will call for "comprehensive and urgent releases".
A Home Office spokesman said: