Washington (CNN) Thirty-four US service members have been diagnosed with traumatic brain injuries following the Iranian missile attack on US forces in Iraq earlier this month, Pentagon spokesman Jonathan Hoffman said Friday.

Seventeen service members who were injured have since returned to duty in Iraq, sixteen of whom were treated locally in the country.

Nine service members are still being treated in Germany. An additional eight service members who had been flown to Germany have since been sent to the United States for additional treatment. The eight service members, who arrived in the US Friday morning, will be treated at Walter Reed National Military Medical Center or at hospitals in their home bases.

Although traumatic brain injuries are not always apparent immediately after they've been suffered, the disclosure of injured US service members indicates that the impact of the attack was more serious than initial assessments indicated.

The Pentagon and President Donald Trump had initially said no service members were injured or killed in the January 8 Iranian missile attack, which was retaliation for the January 2 US drone strike that killed a top Iranian general.

Read More