BEIRUT — Lebanese forces transferred detainees Monday from a notorious jail block where militant Islamists were being held after an investigation suggested that a recent suicide bombing was directed from the facility, the interior minister said.

The clearing of Block B of the Roumieh prison came after years of warnings that the overcrowded section was a meeting point for militants to plot attacks and strengthen networks. Prisoners were known to call into TV shows using mobile phones smuggled into the facility, where many detainees were held without trial.

But political squabbling over the prison north of Beirut kept it untouched, until a groundswell of support for action emerged after suicide bombings on Saturday that killed nine people.

"We have ended the legend that was Roumieh prison," Interior Minister Nouhad Machnouk told a press conference. "All the stories you have heard through the years... of the operations room in Roumieh prison that undertook many terrorist operations in Lebanon, and which is in touch with terrorist bases in the region, has ended today."

As the operation began, some prisoners burned their mattresses and officials said security forces used tear gas. Local reporters said they heard the sound of gunfire, ambulances raced in and out, and helicopters hovered overhead. It was not immediately clear if anyone was seriously wounded in the operation.

Syria's al-Qaida affiliate, the Nusra Front, claimed responsibility for Saturday's attack in Tripoli's predominantly Alawite neighborhood of Jabal Mohsen, saying it was a twin suicide attack. The interior minister said the bombings were carried out by the Islamic State, a rival jihadi group.

"A big part of the operation that happened in Jabal Mohsen was directed from Block B," Machnouk said.

Lebanon has seen several attacks in recent years linked to the war in neighboring Syria, which has exacerbated tensions between Lebanon's Sunnis and Shiites.

Many Sunnis support the uprising against President Bashar Assad, while the powerful Shiite movement Hezbollah has sent fighters to aid his forces. The tensions have paralyzed Lebanon's parliament, making it virtually impossible to address issues like the Roumieh prison.

The Block B prisoners were transferred to Block D, which a security official said was renovated and had better security. The official spoke on condition of anonymity because he wasn't authorized to speak to the media. The interior minister said the government expected to build a better prison to hold the Islamists within three years.