CEDARBURG, Wis. -- A Wisconsin National Guard spokesman said that soldiers who might be questioned about concerns over training procedures have been instructed to cooperate fully with investigators.

The father of a Cedarburg soldier killed in Iraq said that he's received communications from families of other soldiers who share his concerns about inadequate training. Stephen Castner said that the families say their soldiers have been warned by the military that they could be prosecuted for discussing anything to do with training procedures.

Wisconsin National Guard Lt. Col. Tim Donovan said on Tuesday that the commander of Castner's unit, the 1st Battalion, 121st Field Artillery Regiment, recently issued a memo directing his soldiers to cooperate in an investigation into training procedures.

Donovan said that Lt. Col. Scott Rice told his unit that it was their responsibility to do so, without fear of retribution.

Castner had complained to Gov. Jim Doyle and U.S. Rep. Jim Sensenbrenner that his son Stephen received inadequate training before he was killed by a roadside bomb last month.