LAS VEGAS (AP) — Authorities say they are beefing up security for Sunday’s Chicago Marathon following reports the Las Vegas shooter booked a Chicago hotel room during the weekend of a major music festival held across the street.

Chicago Police Bureau of Organized Crime Chief Anthony Riccio said Thursday that there would be “significantly” more undercover officers working the marathon than in years past.

A law enforcement official says Las Vegas gunman Stephen Paddock booked a room at Chicago’s downtown Blackstone Hotel in August.

A spokeswoman for the Blackstone Hotel, Emmy Carragher, says a person with the name Stephen Paddock reserved a room but never checked in.

The hotel overlooks Grant Park where the Lollapalooza festival is held each year and is attended by hundreds of thousands of people.

Riccio says the undercover officers assigned to the marathon “are going to be intermingling with the crowd, they’re going to be around runners, they’re going to be at the finish line, they’re going to be at the start line.”