Many generals and other high-ranking officers in Colombia’s armed forces may have known about a pattern of soldiers killing civilians and passing off the deaths as guerrilla casualties in the campaign against rebel insurgencies, according to a report to be released on Wednesday.

The report, by Human Rights Watch, also says that Colombian prosecutors face numerous obstacles in seeking to investigate high-ranking military personnel who may be linked to the killings, including a lack of cooperation from the armed forces and intimidation of key witnesses.

A scandal over the killings, which were intended to inflate the number of apparent guerrilla casualties and create a false image of positive results in the country’s struggle against insurgents, erupted in 2008. It resulted in the resignation of the commander of the Colombian Army, the firing of a few high-level officers and stained the reputation of the president at the time, Álvaro Uribe, who aggressively escalated the campaign against the guerrillas.

And it also raised questions, which critics say are still relevant, about United States oversight of the human rights record of the Colombian armed forces, Latin America’s largest recipient of military aid from Washington.