Airstrikes were conducted Saturday on the Syrian city that was the site of chemical weapons attack earlier this week, CNN reported.

One person was killed and three others were wounded in the strike on Khan Sheikhoun, the report said. It is not clear who carried out the strikes.

President Trump on Thursday ordered the first U.S. airstrike on the Syrian air force since the country’s civil war began in 2011, in response to the chemical weapons attack earlier this week.

{mosads}Trump defended the strikes, telling reporters that “years of previous attempts at changing Assad’s behavior have all failed and failed very dramatically.”

“It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons,” he said.

The Pentagon on Friday said it was looking into whether or not Russia was involved in Tuesday’s chemical weapons attack that killed at least 70 civilians.