The police did not explicitly say if those arrested had stockpiled the weapons in preparation for an attack similar to the 2017 Las Vegas shooting in which a man fired from his upper-story hotel room at crowds attending a music festival, killing 58 and injuring hundreds.
“We need to identify exactly, to the extent possible, why individuals were here in the first place — why proximity to downtown,” the city’s police chief, Paul M. Pazen, said.
The F.B.I. office in Denver said it did not believe that the arrests were connected to terrorism. “We are not aware of any threat to the All-Star Game events, venues, players, or the community at this time,” it said on Twitter on Sunday.
A spokeswoman for Denver’s Office of Emergency Management also said there was no indication that those arrested planned a mass shooting.
Three of the suspects — Richard Platt, 42; Gabriel Rodriguez, 48; and Ricardo Rodriguez, 44 — were charged with possession of a weapon by a previous offender, the police said. Mr. Platt and Gabriel Rodriguez, along with the woman, Kanoelehua Serikawa, 43, were also charged with possession of a controlled substance with intent to distribute.