A suspicious item found near parliament near the House of Lords was a false alarm.
The City of Westminster Police said the item found on Wednesday had been assessed and deemed “non-suspicious”.
Counter-terror police are still working to identify a motive or suspect over the explosive packages sent to major transport hubs as sorting offices are on high alert for further devices.
Deputy Assistant Commissioner Dean Haydon, the senior national co-ordinator for counter-terrorism policing, said today that no link had been made with Irish dissidents at this stage.
The packages that arrived at Waterloo railway station and offices at Heathrow and London City Airports on Tuesday were posted with Irish stamps and had Dublin as the return address, prompting Irish police to join the investigation.
Police Scotland also said a controlled explosion was carried out as a precaution on a suspicious package found in the mailroom at Glasgow University, after several buildings had been evacuated.
The first report of a suspicious package came from 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 and partially-burn the packaging.
British Transport Police were later called to a suspicious package in the post room at Waterloo station at 11.40am.
The package was not opened and the device was secured.
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.