Eleven U.S. soldiers were treated for concussion symptoms following the Iranian missile attack on Iraqi military bases housing American troops, the U.S. military said.

“While no U.S. service members were killed in the Jan. 8 Iranian attack on Al Asad Air base, several were treated for concussion symptoms from the blast and are still being assessed,” U.S. Central Command spokesperson Capt. Bill Urban said in a statement. “As a standard procedure, all personnel in the vicinity of a blast are screened for traumatic brain injury, and if deemed appropriate are transported to a higher level of care.”

Eight service members were transported from the Al Asad Air Base to Landstuhl Regional Medical Center in Germany, and three were taken to Camp Arifjan in Kuwait for screenings “out of an abundance of caution,” Urban said. The soldiers are expected to return to Iraq after being screened.

The missile attack on Jan. 8 was retaliation for an American drone strike near Baghdad that killed top Iranian military commander Qassem Soleimani. The U.S. military and President Donald Trump’s administration officials initially said there were “no casualties” from the attack.

U.S. troops were warned about the missile strike hours before Iran launched them at the base, the military said on Monday.

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Mahita Gajanan at mahita.gajanan@time.com.