WASHINGTON (AP) — Members of Congress expressed serious concerns Sunday about the safety of Americans at next month’s Olympics in Russia and said Moscow needs to cooperate more on security.

Suicide bombings last month in the southern Russian city of Volgograd, about 400 miles from where the Sochi Games will be held, have contributed to the safety anxiety. Russian President Vladimir Putin has promised that his country will do all it can to ensure a safe Olympics without imposing security measures that are too intrusive.

The State Department has advised Americans who plan to attend the Olympics, which run Feb. 7-23, that they should keep vigilant about security because of potential terrorist threats, crime and uncertain medical care.

“We don’t seem to be getting all of the information we need to protect our athletes in the games,” said Rep. Mike Rogers, chairman of the House Intelligence Committee. “I think this needs to change, and it should change soon.”

But FBI Director James Comey said earlier in January that the Russian government “understands the threat and is devoting the resources to address it.”

Rogers, R-Mich., contended that the Russians “aren’t giving us the full story about what are the threat streams, who do we need to worry about, are those groups, the terrorist groups who have had some success, are they still plotting? There’s a missing gap, and you never want that when you go into something I think as important as the Olympic Games and the security of the athletes, and the participants and those who come to watch.”

Rep. Michael McCaul, chairman of the House Homeland Security Committee, said from Moscow that he planned to be in Sochi on Monday to assess the security situation.

“All the briefings that I’ve received, from the intelligence community to the FBI and others, indicate that there are serious concerns, and that we need to do a lot to step up security. I do believe Putin is doing a lot of that,” said McCaul, R-Texas.

While he said diplomatic security has declared Russian cooperation on safety measures is good, he said “it could be a lot better, and that’s one thing I want to press while I’m over here.”

Comey, the FBI head, told reporters this month in Washington that “we have been in regular communication — including me personally — with their security organizations to make sure we’re coordinating well. I think that we are. We’ve improved our information sharing on counterterrorism and it’s important.”

No one has claimed responsibility for the December bombings in Volgograd. But the blasts followed Chechen warlord Doku Umarov’s call to launch attacks on the Olympics.

“I would not go, and I don’t think I would send my family,” said Sen. Angus King, I-Maine.

An insurgency seeking to create an independent Islamic state in the Caucasus has swept the region after two separatist wars in Chechnya. Chechnya’s Moscow-backed strongman, Ramzan Kadyrov, claimed Thursday that Umarov was dead, but he offered no proof to the claim he had repeatedly made in the past.

The province of Dagestan, located between Chechnya and the Caspian Sea, about 300 miles east of Sochi, has become the center of the rebellion, with daily shootings and bombings of police and other officials.

Rogers appeared on CNN’s “State of the Union” and CBS’ “Face the Nation.” King was on CNN and McCaul spoke on ABC’s “This Week.”