Residents who will be affected by the upcoming NATO summit attended an informational meeting in April. (CBS)

CHICAGO (CBS) — As concerns about security grow in the run-up to the NATO summit, it’s becoming difficult to separate myth from reality.

Are there plans in place for a mass evacuation of downtown in the event of riots on May 20-21? A Red Cross memo out of Milwaukee indicates that there is.

Officials there have been asked to make plans to assist residents in the event of a mass exodus.

Chicago officials say the plan didn’t come from them. The U.S. Secret Service isn’t talking.

There also are reports that a heavily armed security team will start making a very public appearance around federal buildings in the Loop this week. Officials with the Chicago NATO host committee were completely in the dark. They had no reports of any such plans.

A source told CBS 2 that security forces in full battle gear would not be seen this week.

As for the Red Cross plan, CBS 2 News has obtained a copy of an e-mail sent to volunteers in the Milwaukee area.

It said the NATO summit “may create unrest or another national security incident. The American Red Cross in southeastern Wisconsin has been asked to place a number of shelters on standby in the event of evacuation of Chicago.”

According to a chapter spokesperson, the evacuation plan is not theirs alone.

“Our direction has come from the City of Chicago and the Secret Service,” she said.

Officials at Chicago’s Office of Emergency Management and Communication said the directive did not come from them.

The U.S. Secret Service did not return calls for comment.

Some downtown residents told CBS 2’s Mike Parker that the news has them on edge.

Brad Klein said it is “very unnerving. I feel a little bit unsafe, just a bit more than a little bit. It doesn’t make me feel like I want to be in the city during the NATO conference.”

An executive with the Service Employees International Union, who trains members in preparation for the summit, thinks such a plan might be “over the top.”

SEIU Local 1 training director Tom Dobry said, “This could be a lot like Y2K – a lot of hype and buildup. People will say, ‘that was it?’ Not a big deal.”

Chicago residents certainly hope that to be true. But one cannot blame them for wondering exactly what’s going on.

One example happened last week, when protest groups revealed the plans for a security zone around the summit meeting site: McCormick Place.

One major expressway (I-55), Lake Shore Drive, and a large chunk of the lakefront will be closed. The security zone will extend several blocks to the west, south and north of McCormick place. That zone will be completely shut down, they say.

Those protesters came directly from a meeting with the Secret Service when those details were released. However, there was not a single confirmation from the feds.

One thing they have confirmed: Commuter trains will run under McCormick Place during the summit, but the Secret Service said in a statement to “expect delays.”

How bad will those delays get? They aren’t saying.

However, the South Shore will be asking riders to take a survey to determine how many people will even bother coming into the city.

Conductors on the train said the rail agency is trying to determine how many cars to run per train. Since each train car, they say, will take up to eight minutes to undergo a security sweep, they want to run a few cars as possible.

NATO Summit Map