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U.S. investigates friendly fire deaths in Afghanistan

WASHINGTON (CNN) -- The U.S. military has opened an investigation into last week's friendly fire incident in Afghanistan that killed four Canadian soldiers and injured eight others.

The probe, ordered by Gen. Tommy R. Franks, head of the U.S. Central Command, will include findings of fact, opinions and recommendations. Central Command manages U.S. military action in the Afghanistan region.

If the investigation finds any fault or neglect in the incident, it will recommend corrective measures or disciplinary action. Officials estimate the investigation should last between 30 and 60 days.

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Miscommunication is one likely factor in the incident, according to early details from Pentagon sources.

The sources, speaking on condition of anonymity, said Friday that two Air National Guard pilots deployed from a U.S. base in Kuwait were on a nighttime patrol over a recognized training area near the southern Afghan city of Kandahar and reported being threatened by groundfire.

They asked for permission to strafe the area with their aircraft's 20 mm guns but were denied, officials said. Instead, the fliers were allowed to mark the source of the groundfire, sources said.

Turning to mark the location, a pilot again reported groundfire and requested permission to strafe the area, sources said. That request also was denied.

Then, citing rules of self-defense, a pilot dropped a laser-guided bomb on the target, sources said.

Sources said they did not know with whom the pilots were communicating nor whether they had been notified they were flying over an area where a scheduled nighttime "live fire" exercise was under way.

Defense Secretary Donald Rumsfeld said that the Canadian armed services would have "observers" present in every aspect of the probe, vowing it would be "fully transparent to the Canadians."

He said the Canadians would also conduct a "separate but parallel" investigation of their own.