Amtrak officials attributed an “abundance of caution” to Monday’s 45-minute evacuation of Union Station after an unclaimed backpack was found in the building’s center hall.

The facility — which houses shops and restaurants, a Metrorail station and serves as a hub for both commuter and long-haul trains — was evacuated shortly after 12:30 p.m. when a witness reported a “suspicious” backpack near America Restaurant, located near the building’s main entrance.

According to an Amtrak spokesman, who could not confirm whether the item was found by law enforcement agents, the item reportedly emitted “a fuel smell.” Both the D.C. Fire Department and the Capitol Police Department responded to the scene. Officials cleared the item and allowed visitors to re-enter the station shortly before 1:15 p.m.

Dan Stessel, an Amtrak spokesman, said the evacuation was prompted out of “an abundance of caution.”

“In the wake of Madrid, we’re all in a heightened state of vigilance,” Stessel said, referring to the March 11 incident in which bombs detonated on four commuter trains in Madrid, killing about 200 people and injuring 1,500 others. Since that incident, the building has been evacuated about once a week, Stessel said.

According to witnesses, however, some vendors in the building’s basement level food court continued to do business at least five minutes after alarms began sounding. Although no one appeared to panic while exiting the building, one witness said no formal announcement was made, leading to confusion over what was taking place.

During the incident both Amtrak and commuter train service was suspended, but were expected to return to normal schedules this afternoon.