Officials with the NATO-led coalition in Afghanistan say it is too early to tell if the Taliban were behind last week's killing of four French troops by an Afghan soldier.

A spokesman for the International Security Assistance Force said Tuesday that past investigations into similar events have found many different reasons for them.

The ISAF spokesman added that “there are no indicators of a systemic issues of infiltration” by the Taliban into the Afghan security forces and that officials look at this “closely every day.”

Last week's incident appears to be the latest in a series of isolated attacks over the years by members of the Afghan security forces against coalition soldiers.

Afghan and NATO troops often carry out joint operations against the Taliban insurgency and operate in close proximity to each other.