The Cambridge Police Department has released new details about a Saturday morning report of a gunman on MIT’s campus that authorities now believe was a hoax.

In a Tuesday press release, CPD spokesperson Daniel M. Riviello confirmed that the department received the false report via an internet relay, an instant messaging service usually utilized by people who are unable to communicate by regular telephone.

Riviello added that CPD has since been in contact with Sprint, the service provider of the internet relay, which helped CPD to identify a preliminary suspect. According to Riviello, that initial suspect has been cleared of suspicion.

CPD is continuing to investigate the origin of the suspected hoax, and is prepared to press charges against the originator of the false report if that person is found, Riviello wrote.

Riviello also wrote that CPD has been in communication with the MIT Police Department, the FBI, the United States Secret Service, and the Middlesex County District Attorney’s Office as it proceeds with its investigation.

On Saturday, the report of a man with a “long rifle and body armour,” as described in an MIT emergency alert, prompted a campus-wide lockdown. After receiving the report at 7:28 a.m., CPD responded by scouring the building in the Main Group complex on MIT’s campus where the gunman had reportedly been spotted. But after the room-by-room search yielded neither a gun nor a gunman, CPD called off its hunt, and the campus lockdown was lifted at 10:45 a.m.

—Staff writer Matthew Q. Clarida can be reached at clarida@college.harvard.edu. Follow him on Twitter at @MattClarida.