Attleboro District Court officials said documents related to the case, including search warrants, have been impounded, meaning the public can't see them. No charges have been filed.
State police have searched in and around Hernandez's home in North Attleborough several times. At least three search warrants have been issued in connection with the investigation.
Odin Lloyd, who played for the semi-pro Boston Bandits, was found slain June 17. The 27-year-old's relatives said he was dating the sister of Hernandez's fiancee and that the two men were friends.
Hernandez's attorney has said he will refrain from commenting on the substance of the investigation while it is ongoing.
Reporters have been camped out for days at Hernandez's sprawling home on the Rhode Island line, not far from the stadium where the Patriots play. They reported Tuesday that Hernandez got a visit from Boston defense attorney James Sultan.
A spokesman for Michael Fee, the attorney who has been representing Hernandez, said Tuesday that Sultan's firm, Rankin & Sultan, has been co-counsel on the case from the beginning. Among other well-known cases, Sultan helped win a new trial for a former New York banking executive accused of fatally stabbing his former girlfriend on the exclusive island of Nantucket.
The Patriots drafted Hernandez, who is originally from Bristol, Conn., out of the University of Florida in 2010. Last summer, the team gave him a five-year contract worth $40 million.