A passenger jet flying from New York to Moscow made an emergency landing in Iceland on Thursday after a caller claimed there was a bomb on board, a spokeswoman for Russian airline Aeroflot said, according to Reuters.

“There was an anonymous call saying that there was an explosive device on the plane, which was already in the air,” spokesman Irina Dannenberg said. “The pilot took the decision to land the plane and it landed safely. A search is being conducted.”

A spokesman for Iceland’s Keflavik airport said 253 people were on board Aeroflot Flight 103 from New York’s John F. Kennedy International Airport to Moscow’s Sheremetyevo Airport, the plane’s intended destination.

“The bomb threat was made sometime earlier in the morning and at 5:30 a.m. GMT the plane decided to head for Keflavik … The aeroplane landed safely at 6:27 a.m.,” said Keflavik spokesman Fridthor Eydal, Reuters reported.

Russian news agency Interfax, citing an unnamed source, said an anonymous phone call had been made to U.S. law enforcement agencies claiming that five suitcases were filled with explosive materials and that they would detonate upon arrival in Moscow.

Emergency teams also searched for explosives Thursday on a plane in the city of Voronezh, 500 km (300 miles) south of Moscow, after an anonymous phone call was made to the city’s airport, but no bomb was found, state-run RIA reported.