MAZAR-I-SHARIF, Afghanistan (Reuters) – Thirteen soldiers loyal to a northern Afghan warlord were killed and 21 wounded in a huge explosion while they were loading weapons on a truck, police said on Monday. The incident occurred on Sunday evening at Aqcha, a district of Jozjan province not far from the border with Uzbekistan, Mohammad Qoul Zahri, deputy police chief of Jozjan, told Reuters.

He said all the soldiers were loyal to Abdul Rashid Dostum, a northern warlord who is also a defense adviser to President Hamid Karzai.

Zahri said they had been loading the weapons during a disarmament drive by Dostum in the province.

He said the cause of the incident was still unclear and was under investigation, but the most likely cause appeared to have been an accidental detonation.

He said about 800 armaments of different kinds, including rockets and small arms, were being loaded on a number of trucks.

“It was a huge explosion that destroyed five of the trucks,” Zahri said.

He said soldiers from a British military provincial reconstruction team had been invited by Dostum to watch the disarmament operation, but had left the scene before the blast.

The weapons had been handed over by Dostum’s militia fighters as part of an effort to disarm factional fighters in the north, which has been the scene of repeated clashes in the past year.