General Muhammad Daud said on Sunday that 14 people, including some formerly involved with Taliban and the Hizb-i-Islami, were involved in the deaths.
Ten people have so far been arrested over the brutal slayings while the investigation continues, Chinese state news agency Xinhua said.
Quoting General Daud, Xinhua said six more people had been arrested on Sunday.
Earlier in the day the commander, who could not be reached to immediately confirm the report, said four people had been detained and more arrests were to follow.
"There are more suspects soon to be arrested," he said. "Our initial investigation shows that the attackers were 14 people in two vehicles. They are all Afghans."
Daud said those arrested had "been with Taliban and Hekmatyar".
Islamist opposition fighter Gulb al-din Hekmatyar is the leader of the Hizb-i-Islami party which has links with resurgent Taliban fighters.
"There are more suspects soon to be arrested. Our initial investigation shows that the attackers were 14 people in two vehicles. They are all Afghans"
General Muhammad Daud
Hizb-i-Islami is thought to cooperate with Taliban and other government opponents, and is accused of being behind attacks against foreigners and Afghan and US-led occupation soldiers in the past.
Daud refused to comment on statements he reportedly made to Chinese state news agency Xinhua saying the killers were part of a new "terrorist" network.
The Taliban have denied any involvement in the Kunduz killings.
The attack happenned when about 100 Chinese workers were sleeping in their tents which were sprayed with machine-gun fire early on Thursday.
Eleven Chinese and one of two Afghan police guarding the site were killed in the incident.
China has called on the Afghan government and the UN to investigate the assault and bring the "terrorists to justice, and ensure safety and security of other Chinese citizens in Afghanistan", Xinhua said.
Around 400 Chinese nationals are working on road and irrigation projects in the war-ravaged country.