The killers were "indisputably elements from the Coalition of Patriots for Change (CPC)", said Arnaud Djoubaye Abazene, quoting the probe's final report into the March 19 deaths in the centre of the country.
The CPC, an alliance of rebel groups formed in December 2020 to overthrow President Faustin-Archange Touadera, has denied carrying out the killings.
Prime Minister Felix Moloua had accused the CPC of the attack the day after it took place, but offered no evidence.
The CPC denied any involvement in what it described as a "despicable and barbaric" act.
The nine miners had been employed by China's Gold Coast Group at the Chimbolo mine, 25 kilometres (15 miles) from Bambari, the main town in the Ouaka prefecture.
At a press conference, Abazene said he had received the "report of the special commission of inquiry" into the "assassinations" on Wednesday, but journalists at the press conference were not allowed to ask questions.
The murders prompted Chinese President Xi Jinping to call on Bangui to "severely punish" the killers.
A Chinese foreign ministry spokesperson said Xi issued "important instructions, demanding an all-out effort to treat the wounded, handle the aftermath in a timely manner, severely punish perpetrators in accordance with the law, and ensure the safety of Chinese citizens".
Two people were seriously wounded, China added.
The CAR, one of the world's poorest countries, has been in the throes of civil conflict since 2013.
Militias hold sway over large tracts of territory and often clash over access to minerals and other resources.
Russian and Chinese companies dominate mining for gold and diamonds in the Bambari region.