Delta Air Lines said on Monday that “sewing-type” needles were found in sandwiches served on flights from Amsterdam to three U.S. cities over the weekend and that investigators were trying to determine how they got into the meals.

The airline said the needles were found by passengers in four sandwiches on flights from the Dutch capital bound for Atlanta, Minneapolis and Seattle. Kristin Baur, a Delta spokeswoman, said local and federal authorities were investigating the incidents aboard four flights.

She said the airline had taken immediate action with the caterer “to ensure the safety and quality of the food” served on its aircraft.

Christina Ulosevich, a spokeswoman for Gategroup, the Swiss-based company whose Gate Gourmet unit supplies Delta with onboard meals, said the caterer was cooperating fully with investigators.

But she declined to comment further, saying “details of this matter must remain confidential.”

SOURCE: REUTERS