Army counterintelligence officials based in South Korea are looking into who is behind messages that U.S. families and Defense Department personnel received Thursday, telling them they should immediately leave the country.

Americans in South Korea reported receiving fake mobile alerts and messages on social media that they must evacuate the peninsula. It's unknown how many people were affected in the incident or if North Korea was behind it since it recently threatened President Trump and the U.S., the Washington Post reported.

U.S. Forces Korea "did NOT send this message," defense officials wrote in a follow-up Facebook post. "Anyone receiving this false message should not click any links or open any attachments included in the correspondence."

Anyone stationed in South Korea should confirm any order to leave before doing so, the statement added.

The military will investigate to learn if any official defense networks were hacked in order to send the instructions.

Approximately 28,500 U.S. troops are stationed in South Korea, plus thousands more family members. The military has practiced what evacuation of the peninsula would look like.

"If a situation develops quickly and the Department of State requires assistance in the evacuation of noncombatants, the Secretary of State will request that the military assist in the evacuation," the plan states. "During this stage, the military will assemble the noncombatants and then either relocate or evacuate them to a safer place."