"Are they holding a hostage? Currently we cannot confirm this, officially and concisely," Brandet said, referring to the attackers.
Said and Cherif Kouachi are currently barricaded in a printing company office in Dammartin-en-Goele, northeast of Paris, reportedly holding talks with the police.
Earlier, French media reported that the suspected terrorists were holding one person hostage.
On Wednesday morning, alleged Islamic extremists attacked the office of the satirical weekly magazine Charlie Hebdo, killing 12 people, mostly artists. Another 11 were injured. The magazine was known for printing satirical cartoons lampooning prominent figures and organizations, including Islam.
The Kouachi brothers, French nationals of Algerian origin, have been named as the suspected gunmen by the police.