As of late on Thursday, 24 detainees were rejecting food and drink, said Terry Henry, a lawyer for the US Justice Department.
Seven had been hospitalised and were being force-fed through nose-to-stomach tubes. Some of the other 17 detainees also were not eating or drinking, but were in a special cell block and were not yet being fed against their will, he said.
Julia Tarver, the lawyer for a group of 10 Saudi Arabian detainees, said 20-30 suspects were being force-fed.
Lawyers also appeared in court on behalf of five detainees from Yemen and one from Qatar.
At Guantanamo Bay, the US military holds about 500 detainees suspected of links to Osama bin Laden's al-Qaida network or Afghanistan's ousted Taliban government.
The hunger strikers have pledged to starve themselves to death unless they are released or brought to trial. Their lawyers said the detainees might be persuaded by relatives or friends to resume eating and drinking.
But Henry told US District Judge Gladys Kessler that a relative tried to have a lawyer bring into the facility a DVD that named various people who had died or were in jail. That raised concerns about whether some message was being sent.
"There are all kinds of security issues there," he said. Henry also suggested the government did not have the resources to monitor detainee telephone calls.
Lawyers for the hunger strikers also are seeking more frequent access to their clients and copies of their medical records. The lawyers alleged inhumane and cruel treatment at the camp. Some of the detainees have been fasting since 8 August.
Kessler, who at times sounded sceptical of both sides' arguments during questioning, adjourned the emergency hearing without saying when she would issue a decision.