Chicago Marathon

Thousands of runners participate in a past Bank of America Chicago Marathon in Chicago.

CHICAGO — Police say they're increasing security for Sunday's Chicago Marathon after a gunman opened fire on an outdoor music festival in Las Vegas earlier this week, killing 59 people.

The move announced Thursday comes the same day authorities confirmed that Las Vegas gunman Stephen Paddock had booked a hotel room in Chicago during the Lollapalooza music festival in August.

Chicago Police Bureau of Organized Crime Chief Anthony Riccio says there will be "significantly" more undercover officers working during the marathon than in years past. He says the department will increase the number of undercover officers working Monday night when the Bears play at Soldier Field and next week when the Cubs return to Wrigley Field for the National League playoffs.

City officials say they've also met with security staffs of Chicago high rises.

A law enforcement official who was briefed on the investigation and spoke only on condition of anonymity said that while Paddock booked the room at the Blackstone Hotel there is no record of him staying there.

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