The Afghan authorities have launched an investigation to find out the identity of 12 people killed in a US-led coalition bombing raid on Thursday.
The Afghan authorities initially said those killed in south-eastern Paktika province were policemen on patrol.
But a senior Afghan official told the BBC on Friday that the dead "might have been terrorists".
The US military says it is confident the two trucks hit had been used in an earlier attack on coalition forces.
The BBC's Bilal Sarwary in Kabul says the latest deaths will increase pressure on President Hamid Karzai.
On Thursday, parliament approved new Afghan intelligence chief Amrullah Salehi, amid fierce criticism that Afghan intelligence being passed to coalition forces was inaccurate.
Mr Karzai was swift to condemn the raid on Thursday.
He said: "I am extremely saddened by this tragic incident and I want an immediate investigation to find out what exactly happened.
"I have repeatedly asked the coalition forces to take maximum caution while carrying out operations and I want that incidents like this must not be repeated."
The US military responded by saying it was investigating reports that police had been killed and would "work closely" with the Afghan authorities.
On Friday a senior Afghan official told the BBC that "a second investigation has been launched to find out who the people are who have been killed.
"They might have been terrorists," added the official, who spoke on condition of anonymity.
US and Nato forces are fighting the Taleban and its allies in Afghanistan, mainly in the south and east.
US military spokesman Lt Col Paul Fitzpatrick said that the attack in Paktika followed a clash with "extremists" in the Waza Khwa district, in which one Afghan soldier had been killed and a coalition vehicle damaged.
In a separate incident, four civilians were killed in Paktia province on Tuesday night, Afghan officials said.
The deaths occurred after US-led coalition forces came under attack in a village in the Samkani district near the border with Pakistan, provincial police chief Gen Abdul Rahman told the BBC.
The coalition forces returned fire and bombed the village from the ground and the air, killing four people and injuring four others, Gen Rahman said.