A Canadian man charged with stabbing a US airport officer in the neck made references during the attack to people being killed in Syria, Iraq and Afghanistan.
FBI special agent David Gelios, who is in charge of the investigation, said the attack was being treated as an act of terrorism.
Agent Gelios said Wednesday there was no indication at this stage that suspect Amor Ftouhi, who is about 50 years old, was involved in a “wider plot”.
Authorities said Mr Ftouhi stabbed Lieutenant Jeff Neville with a large knife at Michigan’s Bishop International Airport and declared “Allahu akbar”, the Arabic phrase for “God is great”.
Mr Ftouhi also said something similar to “you have killed people in Syria, Iraq and Afghanistan, and we are all going to die”, according to the FBI.
Lieutenant Neville was in stable condition after initially being declared as “critical”.
The attack prompted the airport evacuation and extra security elsewhere in the city northwest of Detroit.
White House press secretary Sean Spicer said President Donald Trump was briefed on the stabbing.
Michigan State Police Lieutenant Mike Shaw said “everything is on the table” as far as a motive for the attack.
He said the regional airport was “shut down and secure” and no other threats had been identified.
Agent Gelios said Mr Ftouhi legally entered the US at Champlain, New York, on June 16.