A Fort Carson brigade is leaving for Afghanistan without its boss, who is being investigated for unspecified violations of Army policy.

The 4th Brigade Combat Team bid farewell to the post in a Wednesday event where commanders ceremonially packed up the unit's flag for the trip. But missing from the rites was brigade commander Col. Brian Pearl, who has been temporarily relieved of his duties during an Army investigation.

"There is an investigation underway within the 4th Brigade Combat Team," Fort Carson said in a statement. "An investigating officer is presently reviewing allegations that violate Army policy, and the actions of everyone involved to include the commanding officer. Until that investigation is complete, no further information will be released."

A source within the unit who wasn't authorized to speak on the investigation said the probe relates to alleged comments by Pearl, but wouldn't give details.

The brigade will be among the last of America's combat troops to serve in the Afghanistan war.

The 4th Brigade probe is the second into alleged misconduct by a Fort Carson commander in the past year.

Col. John McGrath, then the commander of Evans Army Community Hospital, was removed from his duties after a two month investigation that began in August. He was relieved of command and has been serving in administrative duties on the post.

The McGrath investigation concluded "His continual barrage of inappropriate comments and sexual innuendos degrade the command climate and morale."

Investigations are conducted by an officer selected by division leaders who interviews witnesses and compiles a report. The process can take weeks.

Pearl was in command of the brigade as recently as Feb. 18, when he appeared at the head of a formation of 4th Brigade troops in a ceremony to welcome Col. Michael Tarsa as Fort Carson's acting senior commander.

Asked he was ready to head for war after that ceremony, Pearl said, "It can't come soon enough."

In his career, Pearl has earned several top Army decorations, including two awards of the Bronze Star Medal and the Defense Meritorious Service Medal.

Pearl has long experience in the brigade, having led one of its battalions into combat in Afghanistan in 2009. He took over as commander of the 3,500-soldier brigade a year ago.

Pearl has spent the past year readying the brigade for war, leading his troops through a series of training exercises that culminated last fall with a mock war at the National Training Center at Fort Irwin, Calif.

Hundreds of the brigade's soldiers have left for Afghanistan and the rest of the unit is set to arrive there by the end of this month.

The soldiers, for now, will be led by Pearl's deputy, Lt. Col. Daniel Kirk, who said Wednesday that his troops are focusing on their mission in Afghanistan.

"Our upcoming mission will require soldiers in this brigade to do hard things in hard places," Kirk told an audience gathered for the ceremony.

Kirk did not address the Pearl situation and it wasn't mentioned during the Wednesday ceremony.

The brigade has prepared to assist Afghan Forces with a set of training teams. Soldiers also are expected to dismantle the American military infrastructure after 13 years of war and ship gear home.

The last combat troops are set to leave Afghanistan on Dec. 31. While the Pentagon has expressed desire for a continued American presence in Afghanistan, the Afghan government has balked at signing a security agreement.

Defense Secretary Chuck Hagel ordered preparations for a full pull-out last week.