Residents of two villages hit earlier this week by US air strikes have prepared lists with the names of 147 people killed in the attacks.
Farah Province deputy governor Yunus Rasooli told Reuters that residents of the village of Geraani had provided 90 names and residents of neighbouring Ganj Abad village another 57.
The two villages were struck by US warplanes during a battle in another nearby village on Monday and Tuesday.
The issue of civilian casualties is a source of great friction between the Afghan government and its US backers and the air strikes overshadowed a meeting between Afghan leader Hamid Karzai and US President Barack Obama in Washington.
Violence this year has reached its highest level since the Taliban were ousted in late 2001, despite growing numbers of international troops.
The US military plans to more than double its troop numbers in Afghanistan to 68,000 by year’s end.
Officials are still investigating the incident in the two villages and trying to confirm the names, Rasooli said.
If the civilian toll is confirmed it would be the deadliest single incident for non-combatants since US-led forces first started battling the Taliban in 2001.
Rasooli said the lists included eight school children whose names were provided by the ministry of Education.
Abdul Basir Khairkhah, a member of the provincial government’s investigating team, said he had seen two mass graves and more than 40 individual graves in the two villages.
Washington acknowledges bombing the villages during the battle, but US and Afghan authorities have yet to give an official account of the incident, saying the investigation is still under way.