Two senior Republican lawmakers said Thursday that terrorists are already changing their behavior after leaks about classified U.S. data gathering programs, but they offered no details.

Rep. Mike Rogers, R-Mich., said it’s part of the damage from disclosures by National Security Agency contractor Edward Snowden of two NSA programs, which collect millions of telephone records and track foreign Internet activity on U.S. networks. Snowden fled to Hong Kong in May and has granted some interviews since then, saying he hopes to stay there and fight any charges that may yet be filed against him.Rogers said there are “changes we can already see being made by the folks who wish to do us harm, and our allies harm” and that the revelations might also “make it harder to track bad guys trying to harm U.S. citizens in the United States.”

Later Thursday, Sen. Saxby Chambliss of Georgia, the ranking Republican on the Senate Intelligence Committee, used similar language in criticizing Snowden.

“The bad guys are now changing their methods of operation,” Chambliss said. “His disclosures are ultimately going to lead to us being less safe in America because bad guys will be able to figure out a way around some of the methods we use, and it’s likely to cost lives down the road.”

Rogers and Chambliss spoke after closed briefings with top administration officials on the matter.