By Adam Brookes
BBC Pentagon correspondent
The International Committee of the Red Cross (ICRC) says it is worried about a hunger strike inside the US detention camps at Guantanamo Bay.
A British lawyer says hunger strikers have been shackled and fed
The ICRC spokeswoman, Antonella Notari, said the situation there was serious, and her organisation was following it with concern.
But she would not give details of what the ICRC had found during its visits.
The ICRC rarely takes its concerns to the public, but it has done over these hunger strikers.
The US military said that 28 prisoners were on hunger strike.
The military defines a hunger strike as missing nine consecutive meals.
A military spokesman said the hunger strikers were all clinically stable and were receiving nutrition and fluids as needed.
Lawyers for some of the detainees believe that means the hunger strikers are being force fed.
One British lawyer, Clive Stafford Smith, has accused the American military of shackling patients to their beds in order to insert feeding tubes.
Other lawyers have put the number of hunger strikers much higher than the figure given by the US military.
Some say as many as 200 of the 500 or so detainees in the camps have refused food.
Reports of hunger strikes at Guantanamo Bay first surfaced back in July.
The military says some detainees have taken part periodically as a protest against their conditions and then returned to taking regular meals.