The two brothers named by French authorities as chief suspects in the attack on the Charlie Hebdo newspaper in Paris were on the U.S. no-fly list, a senior U.S. counterterrorism official said Thursday.

Another U.S. official said Said Kouachi, 34, has traveled to Yemen. It was unclear whether Kouachi, 34, was there to work with extremist groups like Al-Qaida in the Arabian Peninsula, which is based there.

U.S. officials were tight-lipped about what else they know about Kouachi and his brother Chérif, 32, including whether they fought in the Middle East with extremist groups.

Witnesses said the attackers claimed allegiance to al-Qaida in Yemen.

It would not be unusual for known extremists to be placed on the no-fly list, particularly since Chérif Kouachi had served 18 months in prison for recruiting militants to fight the U.S. in Iraq.

(AP)