German authorities say an investigation of suspected attempts to scope out operations at airports in Germany and France has not turned up any indications that an attack was being planned.

Police stepped up security at airports in southwestern Germany this week after two men were spotted apparently observing security checks in Stuttgart and authorities received a tip about online talk of attack plans. A similar sighting was reported at Paris' Charles de Gaulle airport.

Police said Friday they tracked down the men seen in Stuttgart, who turned out to have been watching a woman they had taken to the airport go through security. Checks on a German man whose car was seen at the Paris airport also produced no evidence of attack plans.

Security was returned to normal levels.