This photo, provided Tuesday, April 4, by the activist Idlib Media Center, shows dead children after a suspected chemical attack in the rebel-held city of Khan Sheikhoun, Syria. Dozens of people were killed, according to multiple activist groups. Edlib Media Center, via AP

A man carries a child at a makeshift hospital in Khan Sheikhoun. Activists have blamed the Syrian regime for the attack. In an apparent reference to the attack, two state-run Syrian media outlets reported that there was an explosion at a "rebel poison gas factory" in the countryside of Idlib province. The government has denied using chemical weapons in the past. Edlib Media Center via AP

A child's body is seen in Khan Sheikhoun. Firas Faham/Anadolu Agency/Getty Images

In this photo provided by the Idlib Media Center, doctors treat a child after the suspected attack. Edlib Media Center via AP

A baby's dead body is covered. Many of the casualties came as a result of asphyxiation, local doctors say. Firas Faham/Anadolu Agency/Getty Images

A dead baby is seen in the aftermath of the attack. "I've never seen anything like it, beyond description," said Fares al-Jundi, a doctor who spoke with CNN. He lives in a nearby village and rushed to the hospital after the airstrikes. Sadduldin Zaidan /Anadolu Agency/Getty Images

Al-Jundi described how whole families were killed: They died of asphyxiation, and foam covered their mouths. Many died suddenly. "I believe this horrible memory will stay with me for the rest of my life," al-Jundi said. Sadduldin Zaidan /Anadolu Agency/Getty Images

An unconscious Syrian child receives treatment at a hospital in Khan Sheikhoun. OMAR HAJ KADOUR/AFP/Getty Images

This photo provided by the Idlib Media Center shows victims of the suspected attack. Edlib Media Center via AP