WASHINGTON — Law enforcement officials became so concerned by President Donald Trump’s behavior in the days after he fired FBI Director James Comey that they began investigating whether he had been working for Russia against U.S. interests, The New York Times reported Friday. The report cites unnamed former law enforcement officials and others familiar with the investigation. The inquiry forced counterintelligence investigators to evaluate whether Trump was a potential threat to national security, and they also sought to determine whether Trump was deliberately working for Russia or had unintentionally been influenced by Moscow. The Times reports that FBI agents and some top officials became suspicious of Trump’s ties to Russia during the 2016 presidential campaign but didn’t launch an investigation at that time because they weren’t sure how to approach such a sensitive and important probe, according to the sources.