http://uk.reuters.com/article/uk-usa-trump-russia-idUKKBN1AJ1ST
The Reuters reports which are also being confirmed by BBC and CNN sources indicate that Robert Mueller's probe is gathering pace, something already indicated by the fact that in recent weeks the Special Counsel's office has been hiring high profile prosecutors rather than investigators.
Anthony Zurcher writing for the BBC says
Now it's deadly serious business. With the news that a grand jury has been convened in Washington DC, and that it is looking into the June 2016 meeting between Donald Trump Jr and Russian nationals, it's clear the investigation is focusing on the president's inner circle.
At the very least it's a sign that Mr Mueller could be on the trail of something big - expanding the scope beyond former National Security Adviser Michael Flynn and his questionable lobbying.
Earlier on Thursday, the US Senate introduced two separate cross-party bills designed to limit the Trump administration's ability to fire Mr Mueller.