In April 2009, in an interview defending her plans to tighten the Canada–US border, Napolitano incorrectly implied that the September 11 attack perpetrators entered the United States from Canada. This claim was made by several politicians based upon erroneous news reports in the days after the attack. Napolitano explained that she misunderstood the question and was referring to other individuals who had planned attacks and entered through Canada, but Canadian diplomats rebuked her for helping perpetuate a myth.