A structure designed to prevent radioactive leakage at the defunct Chernobyl nuclear plant in Ukraine is no longer operational after Russian drones targeted it earlier this year, the U.N.’s nuclear watchdog has found.

The so-called new safe confinement was built as part of a €1.5 billion Europe-led initiative in 2019 to replace the reactor destroyed in the plant’s 1986 meltdown, in which over 30 people died.

But the large steel structure “lost its primary safety functions, including the confinement capability” after a Russian drone strike in February and set its outer cladding ablaze, according to a new report by the International Atomic Energy Agency.

Beyond that, there was “no permanent damage to its load-bearing structures or monitoring systems,” it said.

“Limited temporary repairs have been carried out on the roof, but timely and comprehensive restoration remains essential to prevent further degradation and ensure long-term nuclear safety,” IAEA Director General Rafael Mariano Grossi said in a statement.

The European Bank for Reconstruction and Development is set to provide additional funding for repairs next year.