Ukraine said on Wednesday that nine Russian warplanes were destroyed Tuesday in explosions at the Saki air base in Crimea.

Russia has denied that an attack took place at the base, saying no planes have been damaged and claiming the explosions may have been caused by a smoker who accidentally caused ammunition to catch fire. However, satellite images published Wednesday by Planet Labs PBC show at least seven destroyed fighter planes. The explosions left one person dead and 14 injured.

Ukraine has not claimed responsibility, but if the country’s forces are behind the blasts, “it would be the first known major attack on a Russian military site on the Crimean Peninsula,” The Associated Press writes. In 2014, Russia invaded and annexed the Crimean Peninsula from Ukraine.

Ukrainian military analyst Oleh Zhdanov told AP anti-ship missiles could have been fired at the base, which is at least 125 miles from the closest Ukrainian position. The Institute for the Study of War, a Washington-based think tank, said the Kremlin has “little incentive to accuse Ukraine of conducting strikes that caused the damage since such strikes would demonstrate the ineffectiveness of Russian air defense systems.”