On Wednesday, the House Homeland Security Committee released a report summarizing its investigation into the April 15, 2013, terrorist attack at the Boston Marathon. Among the report’s key findings: Nearly one year after twin backpack bombs killed three people and wounded more than 260 others, U.S. officials are still unsure about the extent of the terrorists’ foreign ties.

Two Chechen brothers, Tamerlan and Dzhokhar Tsarnaev, planted the bombs. There are clear indications that they were inspired by jihadism. But questions have surrounded Tamerlan’s associates since shortly after the attack and those questions have not been fully resolved.