Albanian police have arrested four people and questioned 40 others after armed robbers stole millions of euros from an Austria Airlines aeroplane in a deadly heist.

Armed men broke onto the runway of Tirana airport on Tuesday and stole the money due to be transported to a bank in Vienna, police said.

Foreign banks operating in Albania send their hard currency to Vienna because Albania’s central bank does not accept such deposits.

The robbers entered the runway of the international Mother Teresa airport through a gate used by firefighters.

Police said three armed robbers dressed in military fatigues showed up and threatened the employees handling luggage, eventually stealing the money.

One of the gunmen was killed in an exchange of fire with the police.

According to initial reports, the amount stolen was €2.5m ($2.8m), but local media claimed it could be a five times higher.

Austrian Airlines spokeswoman Tanja Gruber said the cash was being loaded when the robbery happened.

“Boarding had just taken place. There was never any danger for crew and passengers,” she said.

The plane’s departure was delayed by nearly three hours.

As a security measure, there will be no further cash transfers from Tirana to Vienna, she said.

Robbers have staged such heists at least two more times in last three years at the airport.