The FBI is dispatching several dozen agents to Russia to help tighten security at the Winter Olympics.

The FBI is working with Russian intelligence services, said FBI Director Jim Comey. About two dozen agents and other personnel are being sent to Moscow, while more than a dozen others will be assigned to Sochi, the host city of the Games.

“Securing any Olympics is an enormous task,” Comey said. “I think it’s particularly challenging in Sochi because of its proximity to areas of unrest and sources of a terrorist threat.”

Comey said the bureau remains concerned about security at large venues and events generally, reports the Washington Post. Law enforcement officials across the United States, it said, are refocusing their efforts on securing shopping malls after gunmen attacked Nairobi’s Westgate mall in September, killing more than 70 people.

U.S. intelligence indicates that home-grown terrorists continue to be interested in striking “soft targets,” Comey said.

“We are taking a lot of steps with the Department of Homeland Security, state and local law enforcement, and the retail industry to train, to anticipate, to drill,” Comey said. “It was going on before Westgate, and that effort was given renewed energy by the Westgate tragedy.”