FBI examining whether hackers gained access to Clinton aides' emails

But so far, a sampling of senior Clinton aides at the Democratic National Convention in Philadelphia found none who said they had been notified by the F.B.I. or private investigators that their private emails had been compromised. At this point, law enforcement officials say, there is evidence only of attempts to gain access to those associates through “spear-phishing” attacks, often crude efforts to get someone to click on an email that releases malware into the computer.

The committee has said that Russia hacked into its computers and has been supported in its assertion by several private cybersecurity firms, including Crowdstrike, the company that investigated the committee’s breach.

Two years ago, several Clinton aides who had worked at the State Department were notified that their accounts there had been broken into by one of the same Russian intelligence agencies, the Federal Security Service, or F.S.B., suspected of getting into the committee’s system. That hacking, which went largely undetected while Mrs. Clinton was secretary of state in President Obama’s first term, gave the Russian intelligence services what one diplomat termed a road map of Mrs. Clinton’s associates and frequent email partners.