However, U.S. counterterrorism officials say signs point to Lashkar-e-Tayyiba, and they haven't seen anything to rule it out.

CNN: Rice heads to India to ease tensions

Tahawwur Rana, 52, was convicted in June 2011 of conspiracy to provide material support in the plot against the Morgenavisen Jyllands-Posten newspaper and of providing material support to the Pakistan-based Lashkar-e Tayyiba-terror organization.

CNN: Man gets 14 years in plot against Danish newspaper

Reinares, of Madrid's Elcano Royal Institute, said that according to information passed to Spain by several Western intelligence agencies, Megomedov joined training camps in Afghanistan and Pakistan, including camps run by Pakistani militant group Lashkar-e-Tayyiba, after leaving the Russian special forces outfits.

CNN: Spain 'al Qaeda cell' may have targeted Gibraltar