Evidence suggests a deadly explosion at a busy market in the eastern Ukrainian city of Kostiantynivka this month was caused by an errant missile fired by Ukraine, the New York Times reported on Tuesday.

Ukraine has said the Sept. 6 blast, which killed at least 16 people, was caused by a Russian missile.

“Evidence collected and analyzed by The New York Times, including missile fragments, satellite imagery, witness accounts and social media posts, strongly suggests the catastrophic strike was the result of an errant Ukrainian air defense missile fired by a Buk launch system,” the newspaper reported.

Reuters could not independently verify the report.

The press service of Ukraine’s SBU security service, asked about the report, said that according to an investigation still underway, the Russians were responsible for the strike, which it said had involved a Russian S-300 missile system.

“This is evidenced, in particular, by the identified missile fragments recovered at the scene of the tragedy,” it said, adding that the investigation was also examining other materials that pointed to Russian involvement in the shelling.

Ukrainian presidential adviser Mykhailo Podolyak said the circumstances were being studied by law enforcement agencies and that “the legal truth will be established”.