Several United States and coalition personnel were treated for minor injuries after a drone attack in Syria on Friday, a US defense official said, amid heightened tensions in the Middle East.

Personnel were treated for minor injuries, including smoke inhalation, but none were “seriously hurt,” the official said Saturday. “Others are being examined for traumatic brain injuries.”

Several service members were taken from Rumalyn Landing Zone to a separate location for further assessment, according to the official. The attack caused damage to at least one set of facilities, the official added.

“No group has claimed responsibility for the attack,” the official said.

The strike comes after seven US personnel were injured when two rockets hit Al Asad Airbase in Iraq on Monday. The US Defense Department blamed Iran-aligned militia groups for the attack, calling it a “dangerous escalation.”

Those injured in the Monday attack included five US service members and two US contractors. All were stable as of Tuesday, a defense official said.

Both recent attacks come amid heightened tensions in the Middle East, as the US has been bracing for Iranian retaliation against Israel over the assassination of Hamas’ political leader, Ismail Haniyeh, in Tehran last week, CNN previously reported.

US officials have long blamed Iran-backed militia groups for attacks on troops in Iraq and Syria. Between October 17 and January 29, there were more than 150 attacks on US personnel in Iraq and Syria. Those attacks slowed after three American troops were killed in a drone attack on a small US outpost in Jordan, resulting in a significant US response that hit 85 targets at seven locations.