BBC News, Kabul
Five policemen have been killed in Helmand province in the south of Afghanistan in what appears to have been a clash between friendly forces.
American forces have not commented in detail on the incident
Initial reports from the ministry of interior and the deputy police chief for Helmand said American troops had been responsible for the deaths.
The government even went as far as to criticise the US troops.
But the US-led coalition has denied any involvement in the incident and has refused to comment further.
The Nato-led International Security Assistance Force has also denied reports that American troops working under their command had been at the scene.
The government has demanded a "full explanation" into the attack, which it said was "not excusable".
Protests have been held over US forces allegedly targeting civilians
What appears to have happened, based on information from officials who did not want to be named, is that an Afghan National Army (ANA) unit approached a police check point in the village of Spin Kalay, near Gereshk, and was fired upon.
They then returned fire, and in that shooting some auxiliary police were killed and injured.
An American Embedded Training Team vehicle then arrived on the scene.
These are teams of trainers and mentors who work with Afghan forces as part of international efforts to establish a strong Afghan army.
The suggestion is that they did not join in the firing, but arrived in the immediate aftermath.
The question is why the ANA were fired upon by the police.
Auxiliary police units are local people trained up to support the Afghan National Police who are still weak after the decades of war.
They are sometimes little more than local militia, not wearing uniforms and answering to their local commanders - who have pledged allegiance to the government.
Their connections with the Taleban are in places brought into question in the murky world of southern Afghan tribal politics.
The suggestion from officials is that those firing on the Afghan army may well have been consorting with the police.
The lack of accurate information for hours after the incident is an indication of the kind of confusion there is on the ground between multinational and Afghan forces.
It also betrays the complexities of fighting an insurgency labelled with the blanket term "Taleban", but which can be so much more nuanced in reality, tied up in tribal disputes, warlords and the opium trade.