Denmark has closed one of the world’s busiest shipping lanes over an activated but malfunctioning missile launcher on a Danish navy ship, the country’s military said Thursday.

The Niels Juel ship is stationed in Denmark’s Great Belt strait, the main maritime gateway to the Baltic Sea.

The booster on a Harpoon missile on board the ship was activated during a mandatory test on Thursday, and the launcher cannot currently be deactivated, the Danish armed forces said in a statement, adding that specialists are on their way to solve the problem.

“Until the booster is disabled, there is a risk that the missile could launch and fly several kilometers away,” it said.

The danger area is estimated to be up to 5-7 kilometers (around 3-4 miles) from Naval Station Korsør, at a height of approximately 1000 metres above the water in a southern direction, the statement outlined. The missile is not in the direction of the Great Belt Bridge.

The air space in the area is also currently closed, the military said.

“The Harpoon missile is a sharp missile, but it is only the booster that is activated in connection with the test, and there is therefore no danger that the missile can explode or reach further than the booster rocket can lift.”

The police and the Danish maritime authority have been informed, and ships in the direction of the danger zone have been notified and asked to wait until the problem has been resolved, the statement said.