CHICAGO (CBS) — It remains unclear how next month’s NATO summit might impact rail service in the name of security.

As WBBM Newsradio’s Bob Conway reports, Metra officials say they are considering different scenarios to deal with possible service restrictions affecting several rail lines that run under McCormick Place.

LISTEN: WBBM Newsradio’s Bob Conway reports

But just what those scenarios entail is unknown at this point, the Chicago Tribune reports.

Metra spokesman Michael Gillis tells the Tribune it will probably be at least a couple of more weeks before the Secret Service, in charge of security, says what precautions will be imposed.

Any restrictions would affect the Metra Electric District, the South Shore Line and Amtrak, as well as the Canadian National Railway.

The summit takes place Sunday, May 20 and Monday, May 21.