French authorities are converging on a town northeast of Paris as they search for the two brothers suspected of killing 12 people in a terror attack at a satirical magazine.
Cherif Kouachi and Said Kouachi were possibly spotted at a gas station, and were armed and wearing masks.
France's prime minister is worried the Islamic militants may strike again.
Several people connected to the fugitives are in custody. They were arrested during a raid, and one person turned himself in.
French President Francois Hollande ordered flags at half-staff and a moment of silence Thursday to honor the victims.