ST. LOUIS (AP) — Prosecutors say they’re investigating a Twitter post claiming that grand jurors hearing evidence in the police shooting of an unarmed black 18-year-old near St. Louis haven’t seen enough evidence to justify prosecuting the officer.

The Twitter user claimed Wednesday that a friend serving on the grand jury told her the panel lacked evidence to warrant an arrest of Darren Wilson, the white officer who shot Michael Brown on Aug. 9.

The tweet and Twitter account have since been deleted. A county prosecutor’s spokesman says there’s no evidence to suggest information in the tweet is credible.

The AP hasn’t confirmed the poster’s identity.

Grand jurors are expected to complete their work by early November. A juror’s sharing of information from the secret proceedings could amount to misconduct.