From the Washington Post:
Two incidents of “suspicious videotaping” of a European mass-transit system this year prompted a U.S. government warning to domestic homeland security officials this week about possible terrorist surveillance.
The unclassified Department of Homeland Security “public-sector notice” did not describe the incidents or where they occurred, but said they took place in the past 120 days. The bulletin, issued Tuesday, said the episodes provided “indications of continued terrorist interest in mass-transit systems as targets and potentially useful insight into terrorist surveillance techniques.” ….
“There is not specific or credible intelligence at this time suggesting a threat to U.S.-based mass-transit systems,” said Russ Knocke, spokesman for the Homeland Security Department. “We regularly share information with our homeland security advisers and law enforcement partners . . . to continue to encourage vigilance.”