Special counsel Robert Mueller’s team has been rifling through president Trump’s copious array of tweets, the New York Times reports (paywall). The focus is part of a larger probe into whether Trump obstructed justice while the FBI was investigating Russia’s relationship with his campaign.

The special counsel is not likely to point to individual tweets as standalone evidence of obstruction, but to place them in a larger narrative of private and public efforts to meddle with the investigation, according to the Times.

Mueller is reportedly focusing on tweets about fired FBI director James Comey and attorney general Jeff Sessions, plus former deputy FBI director Andrew McCabe. Trump notoriously fired Comey in May 2017, supposedly over Comey’s handling of the investigation into Hillary Clinton’s emails, though Trump later told NBC it was because of “this Russia thing.” Trump was also infuriated that Sessions recused himself from the probe.

Here are a few tweets—including those cited by the Times—that could be clues for Mueller.

Tweets about Comey

Below is the first negative tweet Trump posted about Comey after assuming the presidency. This was six days before Comey’s firing, and followed several interactions in which Comey says Trump asked him for “loyalty” and to “lift the cloud” of the Russia investigation. (Trump has denied asking Comey for loyalty.)

Tweets about Sessions (and McCabe)

Trump was reportedly pushing for Sessions’ resignation in May and July 2017. Some relevant tweets during, and after, those times: