While watching a Detroit Tigers baseball game, 40,000 sports fans were unaware that dozens of police, security guards and federal agents were searching the stadium for a possible bomb after a threat was phoned in to 911, according to an article from The Associated Press.

The crowd was uninformed, and many didn’t learn about the threat until the following day.

After the news was released, the sports fans started asking the major questions that have plagued public event organizers: Should large crowd be informed about unconfirmed threats to their safety?

The threat at Comerica Park was the third bomb threat to a Detroit landmark in less than a week – Monday, someone claimed to have placed a comb on the Ambassador Bridge, and on July 12, a similar threat forced the closing of the Detroit Windsor international tunnel underneath the river. Emergency procedures were carried out correctly, and no bombs were found, AP reports.

On Wednesday, Detroit authorities were trying to determine if the three threats are linked, AP says. No one has been arrested.

In the case of Comerica Park, police followed the stadium’s security protocols, and a decision was made not to evacuate, according to Donald Johnson, an inspector in the police department’s Homeland Security unit.

“We don’t make a decision to evacuate unless an actual device is found,” Johnson said in the AP article. “We don’t panic. We go step by step. The thought was to find out what we actually had.”

According to Lou Marciani, director of the National Center for Spectator Sports Safety and Security (NCS⁴) at the University of Southern Mississippi at Hattiesburg, the goal is not to create a panic.

“Professional sports and many of the major colleges have evacuation plans,” he said in the article. “They do tabletop exercises and refine them all the time. There are pregame processes, in-game processes. If the protocol calls for the movement of people, it would have been done very efficiently in Detroit.”

However, if a bomb had been found, “the decision to evacuated is made for you,” says Steve Layne of Layne Consultants International, a Denver-based firm specializing in the protection of libraries, museums and other cultural institutions or public facilities, in the article. “Then you have to think about if there is staff available to assist moving crowds away from the device, if you have a safe assembly area.”

It is not uncommon for sports stadiums – both college and  professional – to receive bomb threats, but few are evacuated, and the threats are rarely publicized for fear of inspiring copycats, the AP article says.