A training device mistakenly left by a FBI Secret Service contractor at a Washington hotel was the "suspicious package" that prompted a building evacuation.
The FBI and Secret Service sent teams of investigators to the Mayflower Hotel, a few blocks from the White House, after the package was found.
It was a hotel employee who discovered it, said Debbie Weierman, an FBI spokeswoman.
Initially, a spokesman for Washington's fire and emergency management services department said the package appeared to be a hoax.
"It appears to be a deliberate attempt to make people think it was a real device," said Alan Etter. "It was made to look like the real thing."
The 300 people inside the landmark Washington hotel were evacuated.
Etter said the device, which he would not describe, was taken to the basement after it was found.
It was only later - when a Secret Service contractor realized what had happened and called authorities to report the training device - that its source became clear, the law enforcement sources said.
It was not clear to these sources if the contractor was a guest at the hotel, was attending a meeting there or was there for another reason, CNN reports.