The Pentagon said Friday that 34 U.S. service members were diagnosed with traumatic brain injuries stemming from an Iranian missile strike on U.S. troops in Iraq, nearly tripling the number initially reported as injured.

Pentagon spokesman Jonathan Hoffman said eight soldiers who had been treated in Germany were sent to the U.S. for treatment.

Nine others were being evaluated in Germany, he said, while one soldier who was evacuated to Kuwait for treatment had returned to duty in Iraq; 16 who had remained in Iraq after diagnosis have returned to duty.

The announcement came two days after President Donald Trump, who initially said no Americans were injured in the strike, downplayed the extent of injuries among the subsequent 11 cases.

"No, I heard that they had headaches, and a couple of other things, but I would say, and I can report, it's not very serious," Trump told reporters in Davos.

He contrasted the brain injuries with soldiers who lost limbs from roadside bombs in Iraq.

His comments at the time brought a sharp rebuke from some veterans groups. “Don’t just be outraged by #PresidentMayhem’s latest asinine comments,” Paul Rieckhoff, the founder of Iraq and Afghanistan Veterans of America, wrote in a Twitter post that day. “Take action to help vets facing TBIs,” referring to traumatic brain injuries.

US service members injured in Iraq:How soon do concussion symptoms appear?

The Jan. 8 Iranian strikes on bases in western Iraq appeared aimed at avoiding mass casualties among U.S. troops hunkered down there. In the end, there were no fatalities. The missiles were launched in retaliation for a U.S. operation that killed Gen. Qasem Soleimani, Iran's most powerful military commander, in early January.

About 18 hours later after the attack, Trump said in an address to the nation that "no Americans were harmed in last night’s attack by the Iranian regime. We suffered no casualties, all of our soldiers are safe, and only minimal damage was sustained at our military bases."

But "in the days following the attack," 11 people were taken out of Iraq for medical screening, according to a statement from the U.S. Central Command in the region Thursday. "Several were treated for concussion symptoms from the blast and are still being assessed," the statement said.

Concussions are mild forms of traumatic brain injuries. Common symptoms of concussions – headache, memory loss and confusion – may not show up immediately, according to the Mayo Clinic. The symptoms can last for days, weeks or longer.

Concussions are usually caused by a blow to the head. Some but not all concussions can cause victims to lose consciousness.

Experts say it's common for patients not to immediately recognize or report their symptoms.

"At the beginning, when you have the injury, most people are in a hyper-alert state. You're not acutely aware, and you're masking some of the things that might be happening. Subtle changes in memory and concentration – you may not feel them until you are challenged to do an activity," said Pablo Celnik, physiatrist-in-chief at the Johns Hopkins Hospital.

"If you're in the field and being attacked, and there are minor symptoms early on, the adrenaline surge that you get is something that could get you to ignore the early symptoms to deal with the emergency that's in front of you. So you might not immediately report what’s going on," said Daniel Torres, a neurologist at NYU Langone’s Concussion Center. "Sometimes if people have a minor injury, they might think they’ll shake it off."

Contributing: Grace Hauck, USA TODAY