The police were called to investigate suspicious packages near three major transport hubs in London today -- Heathrow and City airports and the city's busiest rail station, Waterloo.
The packages were found in buildings near the airports and within Waterloo itself, although no services were affected.
At Heathrow, police response teams and emergency services attended an incident in the airport's administrative Compass Centre and evacuated the building.
"Heathrow Airport remains operational, flights are not impacted and passengers are able to travel as normal," the airport said. "The police are treating this as a criminal act and we will be assisting with this investigation."
A spokeswoman for the Metropolitan police said the building had been evacuated as a precaution. "Specialist officers attended and the package was made safe," she said.