A military source told journalists on Wednesday that the investigation's conclusions would be presented to the army chief of staff next week.
Israeli public television reported Army chief of staff Dan Halutz expressing regret for "civilian deaths" in the incident, adding that no one had presented an imminent threat - in contrast to previous army statements.
The Israeli daily Haaretz published on Wednesday its own investigation into the incident, which also contradicted the initial version given by the army.
The newspaper report, which was based on eyewitness accounts, said none of the Palestinians who were killed were armed, and said three of them were young people who were not wanted by police for anti-Israeli activities.
An army spokesman had said that five Palestinian resistance fighters including one "high-ranking leader of Islamic Jihad" were killed during the 24 August arrest operation in Tulkarem refugee camp.
The spokesman said soldiers went to arrest rebels after they were tipped off to their presence in a house, but that the Palestinians opened fire and forced soldiers to shoot back.
"All these men were armed and wanted in connection with a 12 July suicide bomb attack in Netanya [north of Tel Aviv], which cost the lives of four Israeli civilians," the army spokesman said.
Shortly afterwards, Islamic Jihad vowed revenge and Palestinian leader Mahmud Abbas slammed the killings, saying they undermined the peace process and a truce being observed by resistance organisations.
"At a time when the Palestinian Authority is trying to maintain calm, this murder intentionally aims at renewing … violence," Abbas said in a statement.