GUANTANAMO BAY NAVY BASE, Cuba -- All four captives who killed themselves at the prison camps for suspected terrorists hanged themselves in their cells with craftily fashioned nooses, a senior officer said Wednesday.

''We've had four individuals commit suicide -- all of them hanging -- three of the four in a cradlelike noose,'' said Navy Capt. Patrick McCarthy, the senior lawyer on the prison camps management team. ``I can tell you that we did not perpetrate the deaths.''

McCarthy made the disclosure in an interview in which he bristled at jokes made about the discovery -- unrelated to the suicides -- of two captives now at Guantánamo wearing contraband underwear. One was wearing a Speedo swimsuit, the other had an unauthorized type of athletic underwear popular with U.S. forces troops called ``Under Armour.''

''There was a Speedo in the camp and someone can hang himself with it,'' he said. ``The Speedo also has a drawstring on it. The drawstring can be used to tie the Speedo, the noose apparatus up onto a vent.''

As staff judge advocate, or senior lawyer, McCarthy is a rare member of the military's senior staff whose tenure at this remote U.S. Navy base in southeast Cuba straddled both episodes -- the simultaneous suicides by three Arabs in June 2006 followed by the lone suicide of a former Saudi Arabian soldier last May.

Prison camp officials had previously refused to describe the circumstances of the fourth man's death on May 30 -- in a maximum-security section of the sprawling detention center called Camp Five, which houses 100 of the 330 or so men held here as enemy combatants.

The means had long been a subject of interest because prison camp tours for media and distinguished visitors emphasize that Camp Five is designed with suicide proofing such as towel hooks that won't bear the weight of a detainee, to prevent him from hanging himself.

Moreover, the tours emphasize that each captive, housed in single-occupancy cell, is under constant Military Police and electronic monitoring, which means a guard is supposed to look in on him at least every three minutes.

The Navy Criminal Investigative Service is still investigating the circumstances of all four deaths.

But McCarthy said he saw all four men dead -- each one hanging -- and that the first three men had used sling-style nooses.

The fourth man, identified at the time of his death as Abdul Rahman al Amri, 31, had fashioned ''a string type of noose'' to kill himself, although he did not elaborate.

The June 2006 triple suicides -- the first ever by a detainee in the Pentagon's showcase detention center -- sent shock waves through the camps and led to changes in procedures, including more careful monitoring of captives' belongings, and the changing of captives' underwear from more elastic briefs to cotton boxers less liable to be used in a hanging.

Navy Rear Adm. Mark Buzby, the detention camps commander, said in an interview Wednesday that the fourth suicide, soon after he took charge, ``reinforced for us the necessity to be extremely vigilant.''

Added Army Col. Bruce Vargo, the military policeman who runs the guard forces: ``You can't stop somebody who is bent on committing suicide. No way you can do it.''

Commanders here have repeatedly said that the two live captives discovered to have the unauthorized underwear were not entitled to the special undergarments under a system that strictly monitors and controls what ''comfort items'' captives may keep in their cells.

It illustrated a breakdown in procedures, and led to a now closed investigation that McCarthy said yielded no explanation about how they got into the tightly controlled prison camps.

The underwear issue came to light in September -- and made international news -- because the military prison wrote a British-American attorney for both men a letter pointing out that his clients' were not entitled to special undergarments. The attorney Clive Stafford-Smith dismissed as ''far-fetched'' the notion that ``we could smuggle in underwear.''

Attorneys' belongings are systematically checked before they meet their client captives, and their notes of attorney-client meetings are taken away by U.S. forces, who submit them to a security review under a process designed by the federal courts in Washington.

McCarthy said he wrote the lawyer after commanders questioned prison camp staff such as guards, health workers and interrogators and could not learn how they received the ''contraband.'' McCarthy declined to say whether he questioned delegates from the International Committee of the Red Cross, who also meet with captives.

But he called the episode troubling, even though the contraband investigation has now been closed.

Until now, Guantánamo officials had little publicly to say about the May 30 suicide, leaving it to other Defense Department officials to characterize it as ''an apparent suicide.'' The military brought in a pathologist from the Miami-Dade County Medical Examiner's office to observe the autopsy, which was never made known and conducted just before Saudi officials traveled to this remote base to accompany home the body of the captive who committed suicide.