Adar Avisar says dozens of flights have been stalled at the country’s main airport near Tel Aviv. It was unclear when flights would resume.

He says the company that supplies fuel to the airport alerted authorities that the fuel might be tainted. The cause was not immediately clear. The spokesman says flying with contaminated fuel can be dangerous.

He said Thursday that all planes undergo meticulous tests before takeoff and there was no chance that flights were currently in the air with contaminated fuel.

Israeli media reported that flights en route to Israel have been asked to refuel in nearby Cyprus before landing in Israel.