WASHINGTON (AP) — A yearlong review of information the U.S. intelligence community had prior to the Boston Marathon bombing found that the investigation could have been more thorough, but the intelligence agencies’ inspectors general said it is impossible to know whether anything could have been done differently to prevent the attack.

The report also said that Russia withheld some information about the bombing suspects until after the attack, but an unclassified version of the report didn’t address what difference that might have made.