The US judge overseeing Donald Trump’s hush-money case in New York City has written a letter to prosecutors and the former president’s defence team about a Facebook post in which a person claims to have known the jury’s decision before it became public.

Justice Juan Merchan’s letter says that on Friday “the court became aware of a comment” on the court’s Facebook page, “now labeled as one week old” from a user named “Michael Anderson”.

“My cousin is a juror and says Trump is getting convicted,” the post says, according to the judge. “Thank you folks for all your hard work!!!”

BBC News has not verified the post, which has been deleted, or the claims allegedly made within it.

The Manhattan District Attorney’s Office and Todd Blanche, Trump’s lead attorney, did not respond to requests for comment.

Justice Merchan did not indicate whether the now-deleted post had been investigated or whether officials suspect any wrongdoing.

Last week, Trump was found guilty of 34 counts of falsified business records. He is due to be sentenced on 11 July.

Justice Merchan’s letter did not specify when exactly the post was made, but he said it was written in response to a 29 May post about oral arguments made “unrelated to this proceeding”.

Trump was convicted on 30 May, one day before the court’s post.

According to US media, the post was made by a now-deleted account that regularly trolls the social media pages of the New York court system.

Because Trump has not been sentenced yet, his defence team could move for the verdict to be set aside temporarily while they investigate the matter. The could also call for a new trial if they can prove that jury misconduct affected the former president’s rights.

Trump’s team might also ask the judge to bring in each juror to question them, in an effort to establish whether any outside influence affected their verdict.

Jurors in the first-ever criminal case against a former US president were under strict orders from the judge not to discuss the case with any outside parties ahead of their verdict.