(CNN) -- Adrian Lamo, the former computer hacker who tipped off federal authorities to WikiLeaks suspect Bradley Manning, says two men in the Boston area have told Lamo in phone conversations that they assisted Manning.

Lamo said both men attend the Massachusetts Institute of Technology, but he refused to identify them because, he said, at least one of them has threatened him. One of these men allegedly told Lamo they gave encryption software to Manning and taught the Army private how to use it, Lamo said.

Manning, an Army intelligence analyst, is being held in solitary confinement at a Virginia detention facility. He is charged with leaking an airstrike video that the whistleblower website WikiLeaks published in April, and Pentagon officials say he is the prime suspect in last week's disclosure of thousands of field reports from the war in Afghanistan to the site.

Lamo claimed both men are working for WikiLeaks. Also, both men are Facebook friends with Lamo and Manning, and at least one continues to post Facebook messages on Lamo's wall, the former hacker said.

Asked for comment about Lamo's allegation that men working for WikiLeaks assisted Manning, WikiLeaks responded in an e-mail: "As a matter of policy, we do not discuss any matters to do with allegations relating to the identity of sources."

The New York Times reported Saturday that Army investigators looking into the document leak have expanded their inquiry to include friends and associates who may have helped Manning. Specifically, the Times spoke to two civilians interviewed in recent weeks by the Army's criminal division, who said that investigators apparently believed that the friends, who include students from MIT and Boston University, might have connections to WikiLeaks. The civilians, who the Times did not name, told the newspaper they had no connection to WikiLeaks.

The Boston Globe interviewed a recent MIT graduate who it said acknowledged Saturday that he met Manning in January and exchanged as many as 10 e-mails with him about security issues. But the individual "adamantly" denied any role in the document leak, the Globe reported. The Globe also reported that this MIT graduate, who spoke on the condition of anonymity, said he was interviewed several months ago by Army investigators to find out whether he or "others in the local computer hacker community" helped Manning.

A spokeswoman for MIT, Patti Richards, told CNN: "We are monitoring the situation closely, but are not commenting at this time."

CNN has previously reported that the FBI is assisting the Defense Department in the WikiLeaks investigation of Manning. One FBI official told CNN the bureau is involved in the investigation of potential civilian co-conspirators who may have played a role in the leaking of the classified material.

Attempts to reach an attorney for Manning have so far been unsuccessful.

CNN's Ashley Fantz, Ashley Vaughan and Shirley Hung contributed to this report.