Passengers and crew on two American Airlines flights arriving from Europe were held away from other travelers upon arrival in Philadelphia on Thursday after several showed signs of "flu-like symptoms," federal officials said.

Customs and Border Protection said 12 passengers on two flights, Flight 755 from Paris and Flight 717 from Munich, showed signs of illness. All 12 have been released after they were reviewed by federal and Philadelphia health officials, CBP said.

The agency said the measure, which is unusual, was taken out of "an abundance of caution" a day after authorities briefly quarantined an Emirates Airline plane upon landing in New York from Dubai. Its crew reported passengers had similar symptoms. The ill travelers in Philadelphia were arriving from the Hajj pilgrimage in Mecca, Saudi Arabia CBP said in a statement.

The American Airlines flights — unlike the Emirates superjumbo jet, which was met with ambulances — were not quarantined. CBP said it examined passengers in a station "away from other passengers." At least 10 passengers were taken to a local hospital after the Emirates flight landed, including seven crew members, the airline said.