Counter-terrorism detectives are investigating a range of possibilities in the hunt for those responsible for sending three explosive devices to major transport hubs in London.
Police responded to suspicious packages at Waterloo railway station and office buildings at Heathrow and London City airports yesterday.
Irish police said they were helping the Metropolitan Police with their inquiries after it was reported that the packages had been sent with Irish stamps.
Workers in London have been warned by police to be vigilant for further suspicious packages.
All the packages were A4-sized white postal bags containing yellow Jiffy bags and appeared capable of igniting a small fire when opened, the Metropolitan Police said.
Scotland Yard said officers are treating the incidents as linked and are keeping an open mind regarding motives.
No-one was injured in the three incidents and no arrests were made.
Officers first received a report of a suspicious package at The Compass Centre, a building near Heathrow Airport’s boundary, shortly before 10am.
Scotland Yard said the package was opened by staff, causing the device to ignite.
The building was evacuated as a precaution and specialist officers attended the scene to make the device safe.
A Heathrow spokesman said flights and passengers were not affected by the incident.
British Transport Police were later called to reports of a suspicious package in the post room at Waterloo station at 11.40am.
The package was not opened and specialist officers secured the device.
The station was not evacuated and trains continued to run as normal but cordons were in place outside in Cab Road.
Shortly after midday, police were also called to a report of a suspicious package at Aviation House at London City Airport.
The package was not opened, the building was evacuated and specialist officers made the device safe. The building reopened.
A spokesman for London City Airport said Aviation House is a staff-only building about three minutes from the terminal and no flights or passengers were affected.
Mayor of London Sadiq Khan said: “Our thanks go to police, security, transport staff and all involved for their swift actions to keep our city safe.”
Metropolitan Police Deputy Commissioner Sir Stephen House told the London Assembly Police and Crime Committee that it was “very early days” in the investigation.
He said advice had been issued to transport hubs across London to be “more vigilant than they normally are” for suspicious packages.
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