U.S Attorney General Eric Holder, left, is welcomed by French Interior Minister Bernard Cazeneuve before the start of an international meeting aimed at fighting terrorism, in Paris, France, Sunday, Jan. 11, 2015.

The United States has yet to determine the party behind this week’s deadly attacks in Paris, U.S. Attorney General Eric Holder said Sunday.

“At this point, we don’t have any credible information that would allow us to make a determination as to which organization was responsible,” Holder said in an interview from Paris with ABC’s “This Week.”

Brothers had training in Yemen?

On Sunday, two senior Yemeni sources said both brothers who carried out the attack against satirical weekly Charlie Hebdo travelled to Yemen via Oman in 2011 and had weapons training in the deserts of Marib, where al-Qaeda has a presence.

This is the first confirmation by Yemeni officials that both Cherif and Said Kouachi, who carried out one of the bloodiest Islamist attacks on the West in years, had visited Yemen where al-Qaeda’s deadliest franchise, AQAP, is based. U.S., European and Yemeni sources had previously confirmed a visit by Said Kouachi.

Meanwhile, AQAP claimed on Friday that it directed the attack against Charlie Hebdo in Paris “as revenge for the honor” of Islam’s Prophet Mohammad.

An AQAP member told the Associated Press in an English statement that “the leadership of AQAP directed the operations and that they had chosen their target carefully as revenge for the honor of the prophet.”

On Friday, the United States issued a global travel warning after the recent terror attacks in France, Australia and Canada.

The alert came hours after French police killed three hostage-takers in a pair of incidents.

Two of the men are believed responsible for Wednesday’s attack on satirical magazine Charlie Hebdo in Paris. Twelve people were killed in that assault, France’s deadliest terror incident in decades.

Asked about the potential activation of terror sleeper cells, Holder said: “I don’t think that we have any information that would indicate, certainly with regard to the homeland, that there is any ongoing threat or any threat that was activated by what we see so tragically here in France.

“With regard to sleeper cells here in France, that is an investigation that’s ongoing and being conducted by our French allies.”

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