Around 20,000 people were evacuated from the city of Balakleya in eastern Ukraine after a massive explosion at an ammunition warehouse at around 3am local time (1am GMT) on 23 March.
The Ukrainian military has said unknown saboteurs blew up the military depot storing about 138,000 tonnes of ammunition, according to Reuters.
Balakleya is about 100km (60 miles) away from the frontline of the conflict between Ukraine and Russian-backed separatists. More than 9,700 people have died in the conflict since 2014.
"According to preliminary data as a result of sabotage, last night at 2.46am (00.46 GMT), fire and explosions caused the detonation of ammunition at several sites storing rockets and artillery weapons," Ukraine's chief military prosecutor, Anatoly Mattios, wrote on Facebook.
He added that a 7km security zone has been set up around the ammunition warehouse. The airspace within a 50km (31 miles) radius of the base has been closed.
Defence minister Stepan Poltorak said that there were no reports of civilians or rescue workers having been injured in the explosion. He added that an investigation is being carried to determine what triggered the explosion, including the possibility of an explosive device being dropped from a drone.
Military spokesperson Yuzef Venskovich told Ukrainian TV network 112 that the same military base was targeted two years ago by saboteurs using drones.
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