A passenger plane from London made an unscheduled landing at Warsaw-Modlin airport in Poland after a bomb threat alert on Tuesday, forcing the airport to close until further notice.

Axar.az reports, citing Reuters, that the airport said in a statement that security services were verifying the reported threat.

“At 9:54 a.m., a bomb threat alert was announced on board an aircraft operating a flight on the route London Heathrow (LHR) – Warsaw Chopin Airport (WAW). At 10:01 a.m., a Boeing 737 MAX aircraft landed at Warsaw/Modlin Airport,” it said.

“Due to the situation, Warsaw/Modlin Airport remains closed until further notice. The services are underway to verify the reported threat and ensure the safety of all people present at the airport.”

There are 181 people aboard the plane, it said. A spokesperson for Polish airlines LOT confirmed it was a LOT flight.