Police have warned commuters in London to be vigilant for further suspicious packages after three explosive devices were sent to major transport hubs.
Counter-terrorism detectives are investigating a range of possibilities in the hunt for those responsible for sending the packages.
Officers responded to suspicious packages at Waterloo railway station and office buildings at Heathrow and London City Airports on Tuesday.
Irish police said they were helping the Met Police with their inquiries after it was reported that the packages had been sent with Irish stamps.
According to the Times, sources said there was currently nothing to suggest that the packages were linked to dissident republican groups, and that the devices did not appear to have intended to cause harm.
Security sources told the Daily Mail that the devices were unsophisticated and suggested that police were looking at whether someone with mental health issues was involved.
Scotland Yard said on Tuesday night that images of two of the packages have been circulated to sorting offices and transport workers.
It said it was working ‘to ensure the safety of the public and staff working at transport hubs and mail sorting offices’, adding: ‘We have shared images of the exterior packaging of two of the devices to aid staff in identifying a potentially suspicious package.’
All the packages were A4-sized white postal bags containing yellow Jiffy bags and appeared capable of igniting a small fire when opened, the Met Police said.
Widely reported images appeared to show the partially burned package destined for The Compass Centre at Heathrow, and another sent to Waterloo.
The stamps appeared to be those issued by the Irish postal service for Valentine’s Day 2018, featuring a heart motif and the words “Love Eire N”.
Both senders’ addresses were given as Dublin, with the one addressed to Waterloo appearing to add Bus Eireann.
The bus and coach operator said police had not been in touch, with a spokeswoman saying: ‘Bus Eireann are currently not aware of this and we have no further comment.’
A statement from Irish police said: ‘An Garda Siochana are assisting the Metropolitan Police with their inquiries.’
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 have been 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, adding: ‘This resulted in part of the package burning.’
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.
One shaken-up man who was among staff outside the Network Rail office said he found that package.
Asked about the discovery, he said: ‘I’m sorry, I’ve been told I can’t talk about it.’
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.
London Mayor Sadiq Khan said: ‘Our thanks go to police, security, transport staff and all involved for their swift actions to keep our city safe.’