A bomb exploded inside a bank in Oregon late Friday afternoon after explosives experts arrived to check on a suspicious object and authorities said at least one person was killed by the blast.

Oregon State Police said the explosion at the West Coast Bank in Woodburn, an agricultural town south of Portland, caused "serious injuries" and that police officers were in the area when the device detonated.

They did not say how many police officers were injured.

A spokesman for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives told the Oregonian newspaper that at least one bomb technician had been injured.

The local county's deputy medical examiner, Rodge Womack, said he has been told of at least one fatality. He said he did not know the identity of the victim.

Some bank employees might have been injured by flying glass but none was seriously hurt, bank CEO Bob Sznewajs said.

Before the detonation, a Wells Fargo Bank branch nearby got a call that was "a potential bomb threat," but police searched and found nothing, Sznewajs said.

He said his bank then got a call "from an unknown person saying that we should look for one as well. We called authorities, but they looked and found nothing."

Sznewajs said an employee subsequently saw a device in bushes near the bank and called the authorities back.

"We looked at it and evacuated the branch and sent people away," he said.

Authorities decided to move the device inside the branch, where they apparently scanned it, and then it went off, he said.

Sznewajs said he didn't know whether the bomb went off on its own or as a result of the technicians' investigation.

He said bank officials had not been allowed back into the building as of Friday night.