Investigators are scrutinizing the recent past of two brothers with al-Qaida sympathies, as a manhunt for the suspects in the newsroom massacre at a satirical French weekly enters its third day.

One of the brothers was convicted of terrorism charges in 2008 and a U.S. official said the other had traveled to Yemen. Investigators are trying to determine whether he was looking to join extremist fighters there.

Twelve people died in Wednesday's attack on the Charlie Hebdo newspaper. It was France's deadliest terror attack in decades. French officials are holding a crisis meeting Friday morning.

Police SWAT teams late Thursday swarmed a region north of Paris, fearing a second strike by the suspects, who are described in a nationwide notice as "armed and dangerous."