Yemeni authorities were hunting for 10 of the main suspects in the 2000 bombing of the USS Cole after they escaped from prison Friday, officials said.
The fugitives, including chief suspect Jamal al-Badawi, were jailed in the tightly guarded intelligence building in the port city of Aden since shortly after the destroyer was bombed, killing 17 American sailors.
Officials close to the investigation said the men fled through a window they smashed inside the building.
The officials said on condition of anonymity that prison officers gave the men permission to go to the prison courtyard for their daily morning break before they escaped.
It was unclear whether the escapees received any assistance from people inside or outside the prison.
Photographs of the men were distributed to police and houses of the escaped men's relatives were searched, the officials said on condition of anonymity.
The Oct. 12, 2000, attack on the Cole was blamed on Usama bin Laden's Al Qaeda network.
Al-Badawi allegedly helped buy the dinghy used by the two suicide bombers, who rammed the destroyer as it was refueling in Aden.
The 10 men, some of whom are believed to be linked to Al Qaeda, were part of a 17-man group arrested after the Cole bombing.
Officials said that the men might have left Aden and headed to Al Qaeda strongholds in the northern province of Shabwah.
Last July, Walid Abdullah Habib, a Yemeni member of Al Qaeda who was arrested while trying to enter the country illegally, escaped from prison.
Habib was arrested this year in a desert area near the Oman-Yemen border and handed over to Yemeni authorities. Habib is from Shabwah.
Yemen, the ancestral home of bin Laden, has been a hotbed of terrorist activity. Islamic militants from here have fought in Afghanistan and Chechnya.
Supporters of Al Qaeda have claimed responsibility for several bombings targeting security officials and government offices in the past few months.
Yemen committed itself to joining the war on terrorism following the Sept. 11 attacks in America and has allowed U.S. forces to enter the country and train its military.
Friday's escape was not the first time a top terrorism suspect has busted out of a Yemeni prison.
Last July, Walid Abdullah Habib, a Yemeni from Shabwah belonging to Al Qaeda, escaped from prison after being initially arrested while trying to enter the country illegally.