Kashmiri Muslim girl reads the holy Quran (AP)

WASHINGTON (AP) -- A spokesman for the international military force in Afghanistan says findings from an investigation into the burning of Muslim holy books at a NATO base may come out as early as Wednesday.

German Brig. Gen. Carsten Jacobson told reporters at the Pentagon by video-teleconference from Kabul that Afghan authorities joined the probe of what he called a mistaken burning of religious materials, including Qurans.

He said the incident, which led to two days of demonstrations across Afghanistan, has "grave implications" for the war effort. He stressed that the burning was an error and that those responsibility will be held accountable.

Jacobson said the findings of the investigation should be known by Thursday at the latest and that the international coalition would issue a "very clear statement" of what happened.