London's King's Cross St Pancras Tube station was evacuated over a "fire alert" on the same day parcel bombs were discovered at Heathrow, Waterloo and London City airport.
Transport for London (TfL) tweeted that the station was closed and no trains were stopping while they investigated the incident shortly before 9.45pm on Tuesday.
Kings Cross and St Pancras mainline stations remained open and tickets were accepted on local buses.
Gur Samuel tweeted an image of a crowd of people standing in front of closed gates at the station.
He said: "Just got evacuated off the tube at St Pancras. Station's shutting now."
Kelvin Chan tweeted: "Staff are kicking everyone out and saying it’s an emergency."
The station reopened just a short while later at about 10.05pm.
The city was on high alert as counterterror officers investigated three devices left in packages at transport hubs across London on the same day.
A Scotland Yard spokesperson described the packages as A4-sized white postal bags containing yellow Jiffy bags.
Officers were first called to reports of a suspicious package at the Compass Centre, an office building in the grounds of Heathrow airport, shortly before 10am.
The second device was reported at 11.40am, when British Transport Police were called to investigate a suspicious package in the post room at Waterloo railway station.
The third device was reported shortly after midday at Civil Aviation House, an office building next to London City airport in east London.
