The fire erupted at the munitions depot in the town of Balakliya in the Kiev-controlled part of eastern Ukraine.
Ukrainian authorities have blamed the fire, which broke out Thursday, on an "act of sabotage" and opened probes into possible "diversion" or negligence of military personnel.
"The body of a woman born in 1951 was recovered from under the debris of a collapsed house," the head of Ukraine's emergency service Mykola Chechotkin said Friday, Interfax Ukraine news agency reported.
The fire erupted at the munitions depot in the town of Balakliya in the Kiev-controlled part of eastern Ukraine, setting off several blasts that injured one and forced authorities to evacuate thousands of people.
Ukraine has temporarily closed the airspace in a 40-kilometre (25-mile) radius around the arms depot, Deputy Infrastructure Minister Yuriy Lavrenyuk wrote on Facebook.
The detonating munitions have prevented firefighters from putting out the blaze but the number of explosions has now "substantially decreased", the defence ministry said Friday in a statement.
Ukrainian Prime Minister Volodymyr Groysman on Thursday warned that the fire could take up to a week to extinguish.
Defence Minister Stepan Poltorak said authorities were considering a theory that the fire was caused by "explosive devices dropped from an unmanned aerial vehicle", Interfax Ukraine news agency reported.
President Petro Poroshenko ordered increased security controls at the nation's military facilities, presidential spokesman Svyatoslav Tsegolko said.
The Ukrainian military has been fighting pro-Russian separatists in the country's east since April 2014 in a conflict that has killed more than 10,000 people.
The depot in Balakliya housed munitions and arms used by Ukrainian troops fighting the insurgents, according to Ukrainian television.