Three men and a woman were arrested and 16 long guns, body armor, hundreds of rounds of ammunition and narcotics were seized from two rooms at the Maven Hotel in downtown Denver.
The discovery initially prompted police to suspect they had thwarted a possible mass shooting plot in the works. But on Sunday morning, FBI officials in Denver said a preliminary investigation has not turned up any evidence that the episode was tied to terrorism.
"We have no reason to believe this incident was connected to terrorism or a threat directed at the All-Star Game," the FBI Denver field office said in a statement. "We are not aware of any threat to the All-Star Game events, venues, players, or the community at this time."
The FBI said it is working closely with the Denver Police Department, the lead investigative agency of the incident, to get to the bottom of why the cache of weapons ended up at the hotel.
A preliminary assessment indicated the stash of guns appears to be connected to a possible illegal transaction involving drugs and guns, according to an internal law enforcement memo obtained by ABC News.
But Denver Police Chief Paul Pazen said at a news conference Sunday afternoon that the investigation is in its early stage and that "nothing has been ruled out."
“We don’t know what we don’t know," Pazen said. "That’s what the investigation is all about. We need to identify exactly, to the extent possible, why individuals were here in the first place, why in proximity to downtown. We don’t have those answers."
Pazen added, "What I can say is that through the great work of the staff at the Maven and the great work by our officers that this is a safer city. Taking guns off the street, taking narcotics off the street is a good thing for the people of Denver."
With the national spotlight on his city, Denver Mayor Michael B. Hancock attempted to reassure residents and visitors that the city is safe.
"Our No. 1 priority is the safety and well-being of everyone who is in our city enjoying our great city," Hancock said at a press conference Sunday. "I want to assure the public today that because of the swift work of our police department, the situation is under control."
The four people arrested were identified by authorities as Richard Platt, 42; Gabriel Rodriguez, 48; Ricardo Rodriguez, 44, and Kanoelehua Serikawa, 43. The suspects were being held on suspicion of weapons charges and possession of a controlled substance with intent to distribute, according to Denver police.
Gabriel and Ricardo Rodriguez, who are suspected of being convicted felons in possession of weapons, were being held without bond, police said. It is not immediately clear at this time whether the suspects have lawyers.
Platt made his first appearance in court on Sunday and a judge ordered him to remain in jail in lieu of a $50,000 cash bond. The other three suspects were waiting to be assigned defense attorneys are expected to appear in court on Monday, officials said.
SWAT teams and numerous other police officers converged on the Maven Hotel around 7:30 p.m. local time on Friday after a housekeeper at the hotel saw a rifle in one of the rooms being cleaned and reported it.
Denver police said they obtained search warrants and spent several hours Friday searching rooms on the fourth and eighth floors of the hotel, where the weapons and ammunition were found. Illegal drugs were also found in at least one of the rooms, police said.
"The investigation and arrests were the result of a tip from the public, serving as an excellent example of the critical role the community plays in public safety," Denver police said in a statement, adding that the agency encourages residents and visitors "to always be aware of their surroundings and to report suspicious or illegal activity to police immediately."
The Sage Hospitality Group, which operates the hotel, praised the police and its own staff for the quick response.
"We are incredibly proud that our team swiftly alerted the authorities in this instance," the Sage Hospitality Group said in a statement. "We are thankful to DPD for their quick action to safely resolve this situation and will continue to work closely with them to support their investigation."
The incident came as thousands of baseball fans poured into Denver for festivities surrounding the All-Star Game, including the annual home run derby scheduled for Monday night.