In a lawsuit filed Tuesday in the Southern District of Florida, Brown was accused of sexual assault on three separate occasions including rape in 2018 by a former trainer.
Brown has denied the allegations. Darren Heitner, a lawyer representing Brown, told The Associated Press on Tuesday his client plans to countersue.
"On Antonio's situation, both Antonio and his representatives have made statements and so I'm not going to be expanding on any of those," Belichick said. "They are what they are. We've looked into the situation, we're taking it very seriously. All the way through the organization. I'm sure there are questions, but I'm not going to be entering any discussion about that."
NFL Network Insider Ian Rapoport reported during Wednesday's NFL NOW that league's investigation into Brown will be "handled as quickly as possible." Brown's accuser has indicated a willingness to speak with the NFL, but Rapoport reported it is unclear whether an interview will be conducted this week or next week.
"As far as what the NFL can do here, they can put Antonio Brown on the Commissioner's Exempt List. It is an option," Rapoport said. "It is something that the league is considering, but it is unclear at this point if it is something the league will do. As far as my research shows, I have not found another instance where someone charged in a civil matter was put on the Commissioner's Exempt List. That would certainly set new precedent here."
A player on the Commissioner's Exempt List cannot practice or attend games, but is allowed at the team's facility for meetings, individual workouts, therapy and rehabilitation and other permitted non-football activities if permitted by the franchise.
Both NFL Media and the AP do not ordinarily name the alleged victims of sex assaults, but Britney Taylor was identified in the federal lawsuit and was quoted in a statement provided by her lawyer, David Haas.
"As a rape victim of Antonio Brown, deciding to speak out has been an incredibly difficult decision," Taylor said. "I have found strength in my faith, my family, and from the accounts of other survivors of sexual assault. Speaking out removes the shame that I have felt for the past year and places it on the person responsible for my rape."
"We're taking it one day at a time. Just like we always do," Belichick said when asked about Brown's Week 2 status.
Rapoport reported Wednesday that neither the NFL nor the Patriots were aware of the allegations against Brown or a pending lawsuit when they signed him Saturday.
"I'm not going to be expanding on the statements that have already been given," Belichick said on the matter.
Brown's agent, Drew Rosenhaus appeared on ESPN's SportsCenter and said "these allegations are false."
"He denies every one of them," Rosenhaus said. "I am very confident that his legal team has facts that will prove this."