Guantanamo Bay Naval Base, Cuba ? The U.S. military transferred the first group of detainees Thursday to a new maximum-security prison at Guantanamo Bay designed to restrict contact among the prisoners and prevent attacks on guards.

More than 40 detainees were brought to the $37 million prison perched on a plateau overlooking the Caribbean Sea from another maximum-security facility at the U.S. naval base in eastern Cuba, said Navy Cmdr. Robert Durand.

The 178-cell prison, constructed beside another maximum-security prison built in 2004, will allow the base to phase out an older facility, Durand said.

U.N. human rights investigators and foreign governments have called on the U.S. to close the entire detention center because of allegations of abuse of detainees by guards. The United States labels Guantanamo detainees “enemy combatants,” which accords them fewer rights than other prisoners.

About 430 men currently are held at Guantanamo on suspicion of links to al-Qaida or the Taliban, including about 100 who have been cleared for release and are awaiting transfer to another country. Fewer than a dozen inmates have been charged with crimes.

The new prison originally was designed as a medium-security facility. But the military made several modifications, citing concerns raised by three suicides in June and a clash in May between guards and detainees armed with makeshift weapons.

It is now one of two facilities reserved for prisoners who are least compliant – an assessment the military says it bases on detainees’ adherence to base rules rather than their cooperation with interrogators.

Detainees will be confined in individual cells with long, narrow windows overlooking areas with metal tables and stools that were meant to be shared spaces but now will be off-limits.

An open-air recreation area has been divided into smaller spaces, which will hold only one detainee at a time. Shower doors were redesigned to allow guards to shackle prisoners’ hands and feet before they leave the stalls, and fencing was installed on second-tier catwalks to prevent detainees from jumping over the sides.

The new prison also has air conditioning, a medical center and two rooms that will allow detainees to meet privately with their attorneys, Durand said.

U.S. Navy Cmdr. Kris Winter said the modifications will help make guards safer. In the last year and a half, the military has recorded more than 430 incidents in which detainees have thrown “cocktails” of bodily excretions at guards, as well as 225 physical assaults.