Updated

A KLM Royal Dutch Airlines (search) flight from Amsterdam to Mexico City was blocked mid-flight by U.S. authorities for having two undesirable people on board, the airline said Sunday.

KLM spokesman Bart Koster said the flight was approaching the U.S. border from Canada (search) when the pilots was told they would not be allowed to enter U.S. airspace because of the two passengers who were considered a risk, apparently due to terrorism fears. Their names were not released.

The flight turned around and went back to Amsterdam (search). A new flight traveled as normal on Saturday, without the two problem passengers, Koster said.

It was not known what happened to the two travelers who were barred.

"They weren't suspected by the Dutch authorities or on European no-fly lists," he said. "I guess they went their way."

Kosters said the incident was unusual, since U.S. and European no-fly lists are usually the same.