MIAMI (AP) - More prisoners have joined a hunger strike at the U.S. military prison at Guantanamo Bay, officials said Monday, as defense lawyers expressed alarm about one of the most sustained protests at the base in several years. There are 28 prisoners on hunger strike, up from 21 a week earlier, including three who were hospitalized for dehydration from refusing to eat, said Navy Capt. Robert Durand, a spokesman for the prison on the U.S. base in Cuba. The military is force-feeding 10 of the prisoners to prevent dangerous weight loss, Durand said. Lawyers for prisoners have been returning from visits to the base with reports that the hunger strike is much more widespread, involving a majority of the 166 men held there, and that some have lost significant weight in recent weeks. Army Capt. Jason Wright said an Afghan prisoner who goes only by the name Obaidullah has dropped from about 167 pounds to 131 since he went on strike and appeared dizzy and fatigued as they met last week. "He seemed depressed, frustrated at the worsening conditions of his confinement," Wright said. It seemed like he didn't have any hope of getting out of Guantanamo Bay. A prisoner from Syria, Abdehhadi Faraj, has lost about 30 pounds and has been having severe stomach pain, migraines and dizziness and vomiting blood, according to Ramzi Kassem, an attorney and law professor at the City University of New York, who visited him last week. He said one of his clients from Yemen has lost a similar amount of weight and that only a handful of prisoners are not participating in the strike. A Kuwaiti prisoner, Fayez al-Kandari, has also lost significant weight and has trouble standing, according to his lawyer, Carlos Warner, a federal public defender based in Ohio. "He's in rough shape," Warner said. I think if they let this go another month or two we are going to see some deaths. The U.S. military has a formal definition of what constitutes being on hunger strike that includes missing nine consecutive meals, which may explain some of the difference between the official tally and the accounts from defense lawyers. Durand said some men may be pretending to take food to prevent being listed as a hunger striker or force fed. The medical staff is closely monitoring the weight and health of all prisoners, he said. Some prisoners have covered up the security cameras in their cells to make it more difficult to track their eating, he said. "I don't know how that will be resolved but it is a matter of concern for the safety of the detainees," he said. The hunger strike began on Feb. 6 and was prompted by what the prisoners considered more intrusive searches of their cells and of the Qurans that each man is issued by the government as well as their open-ended confinement without charge. Military officials say there has been no change in the way searches are conducted at Guantanamo and the hunger strike is an attempt to attract media coverage. A delegation from the International Committee for the Red Cross was making one of its regularly scheduled visits to Guantanamo this week and members were expected to meet with hunger strikers. Its findings will be sent to the prison's commander and to the Miami-based U.S. Southern Command, which oversees the detention facility, but will not be made public. Hunger strikes have occurred at Guantanamo since shortly after it opened in January 2002.