The woman, understood to have arrived from Sierra Leone, was being held at Dungavel Detention Centre in South Lanarkshire.
She fell ill and was taken to hospital to undergo tests, including for the deadly virus which is affecting large parts of west Africa.
The Home Office had suspended the detention or release of detainees from Dungavel while the investigation was carried out. Staff and visitors were still allowed in and out of the centre.
NHS Lanarkshire said the tests were a precautionary measure and in a statement yesterday added that it was "highly unlikely" that the patient would have Ebola.
The latest negative test comes after a Sierra Leone athlete competing at the Commonwealth Games was tested and found to be clear of Ebola in Glasgow last month.
So far more than 1,000 people have died and almost 2,000 suspected, probable or confirmed cases have been recorded in west Africa since the outbreak was first detected. Health leaders have said it could take six months to get the spread of the disease under control.
Ebola is transmitted by direct contact with the body fluids of a person who is infected.