WASHINGTON (AP) — A review of how the government's intelligence agencies handled information they had before the Boston Marathon bombings last year concluded that it was impossible to know whether anything could have been done differently to prevent the attack.

Whether information withheld by Russia until after the bombings could have made a difference was not addressed in the unclassified version of the report.

Three people died and more than 200 others were injured in two explosions during the Boston Marathon. Two ethnic Chechen brothers are accused of carrying out the attacks.