Journalists working for AP said US troops erased images of a vehicle in which three people had been shot dead.
The US military said it could not confirm its troops had seized any film.
Afghans who were wounded in the attack say American soldiers opened fire on civilian cars and pedestrians on a busy highway. As many as 16 people died, though it is unclear whether the bullets that killed them came from Americans or militants (or both).
As the Americans sped away, they treated every car and person along the highway as a potential attacker, said Mohammad Khan Katawazi, the district chief of Shinwar. But Maj. William Mitchell, a U.S. military spokesman, said those killed and injured may have been shot by the militants.
More than a half dozen Afghans recuperating from bullet wounds told The Associated Press that the U.S. forces fired indiscriminately along at least a 10-kilometer (six-mile) stretch of one of eastern Afghanistan's busiest highways — a route often filled not only with cars and trucks but Afghans on foot and bicycles.
"They were firing everywhere, and they even opened fire on 14 to 15 vehicles passing on the highway," said Tur Gul, 38, who was standing on the roadside by a gas station and was shot twice in his right hand. "They opened fire on everybody, the ones inside the vehicles and the ones on foot."
It is not known how much, if any, of the images or recordings of the incident and aftermath remain intact. For its part, the Associated Press (AP) said it "plans to lodge a protest with the American military". To wit:
A freelance photographer working for AP and a cameraman working for AP Television News say they arrived at the site about half an hour after the suicide bombing.
Witnesses at the scene said three civilians in the four-wheel drive vehicle had been killed by US forces fleeing the attack, the journalists said.
"When I went near the four-wheel drive, I saw the Americans taking pictures of the same car, so I started taking pictures," photographer Rahmat Gul said.
"Two soldiers with a translator came and said, 'Why are you taking pictures? You don't have permission.'"
Mr Gul said troops took his camera, deleted his photos and returned it to him.
His APTN colleague, who did not want to be named, said he was told he could film the scene - but when he did so a US soldier got very angry and deleted any footage that included the Americans.
Khanwali Kamran, a reporter for the Afghan channel Ariana Television, said the American soldiers also deleted his footage, AP reported.
"They warned me that if it is aired ... then, 'You will face problems,'" Mr Kamran was quoted by the news agency as saying.
Reporters Without Borders condemned the alleged actions of the US forces, saying they dealt with the media poorly.
There are times when even I am at a loss for words, and this is one of them.
Also at Ezra's place.