Lieutenant Jeff Neville had worked for more than 20 years as a law enforcement officer
A police officer is in hospital recovering after he was stabbed in the back and neck at an airport in Michigan, police say.
A suspect is in custody after Wednesday morning’s attack at Bishop International Airport in Flint.
The FBI, which is leading the investigation, said it cannot rule out terrorism as a motive.
The attacker cried "Allahu Akbar" ("God is greatest"), witnesses and sources at the airport were quoted as saying.
"We are aware of reports that the attacker made statements immediately prior to or while attacking the officer," the FBI said in a statement.
More than 100 passengers and employees were stranded on the pavement as investigators searched the airport Police with sniffer dogs are searching the evacuated airport
"But it is too early to determine the nature of these alleged statements or whether or not this was an act of terrorism."
The airport has been evacuated and additional officers have been stationed at city hall, officials say.
The officer appears to have been targeted, police told journalists.
He was named by local media as Lieutenant Jeff Neville, and was in a stable condition.
"Please keep the officer in your prayers," said Michigan State Police on Twitter.
Multiple media outlets have reported that the attacker is a Canadian passport holder, and a resident of Quebec.
Lt Neville was standing at the top of the escalators when he was approached from behind and attacked with a large knife, sources told ABC 12 in Flint.
The incident took place shortly after 09:00 local time (13:00 GMT) on Wednesday.
Flint Mayor Karen Weaver said in a statement: "My thoughts and prayers are with all of our law enforcement officers who work to service and protect us each and every day.
"I want the public to know that several agencies are involved and working to ensure the situation is under control."
They are taking extra precautions just to be safe, she added.
Police Chief Tim Johnson has asked mass transit officials to be on notice for any further potential incidents.
The mayor’s chief of staff, Steven Branch, said there is added police presence at the city’s water treatment plant, WNEM-TV reports.
US President Donald Trump has been briefed on the incident by his Homeland Security advisor, White House press secretary Sean Spicer told reporters.
Officials say the airport will remain closed until further notice.
About 800,000 passengers used the airport last year.