They had help

VOANews.com has an article about al-Qaeda in Yemen:

Security officials in Yemen say about 60 al-Qaeda-linked militants have escaped from a southern prison after gunmen attacked the facility. Officials say the attackers and escaping prisoners clashed with guards at the prison in Mukalla, leaving one guard dead and two others wounded.
The escape came as a senior U.S. envoy met in Sana'a with Yemeni officials to push a Gulf Arab initiative to end a political stalemate paralyzing Yemen's government. The plan calls for President Ali Abdullah Saleh, who is recovering in Saudi Arabia from an attack on his palace compound, to leave office, but Mr. Saleh has waffled on the plan. Yemeni media say envoy Jeffrey Feltman, the U.S. Assistant Secretary of State for Near Eastern Affairs, met with several high-ranking government figures and opposition members in the Yemeni capital.
Washington is growing concerned about increased activity by Islamic militants in Yemen as the country struggles with a broader opposition uprising against President Saleh. Insurgents have launched several attacks in southern Yemen during the country's political unrest. Military officials said clashes killed a dozen al-Qaeda-linked militants and at least two Yemeni soldiers outside the city of Zinjibar. Armed militants also renewed attacks earlier this month against government buildings near the town of Houta.