Like a dog with a bone:

Special Counsel Robert Mueller and his prosecutors haven’t concluded their investigation into whether President Donald Trump or any of his associates helped Russia interfere in the 2016 election, according to a person with knowledge of the probe.

Friday’s indictment of a St. Petersburg-based “troll farm” and 13 Russian nationals should be seen as a limited slice of a comprehensive investigation, the person said. Mueller’s work is expected to continue for months and also includes examining potential obstruction of justice by Trump, said the person, who requested anonymity to discuss an investigation that is largely confidential.