Meanwhile, Essex Police was called to the University of Essex in Colchester on Wednesday afternoon, placing a 100m cordon around the premises and evacuating a section of the university and nearby buildings.
Meanwhile the University of Glasgow evacuated several buildings on the main campus "as a precautionary measure" after a suspicious package was found in the university's mailroom.
Lectures were cancelled but the university said it was expected to be open as usual on Thursday.
Tuesday's suspicious packages were found at an office block next to Heathrow Airport, the post room at Waterloo station, and at offices near London City Airport in the east of the capital, according to Scotland Yard.
Police Scotland Assistant Chief Constable Steve Johnson said that the package found at Glasgow University was not opened and no one was injured.
USA trade deficit hits 10-year high despite tariff war
Globally, the trade deficit jumped from $796 billion to $870 billion between 2017 and 2018, an increase of $74 billion. Simultaneously, other countries - including China and members of the European Union - have not been doing so hot.
Body of missing Sydney dentist found in suitcase
The 32-year-old from Penrith in western Sydney had been attending a dental convention at St Leonards over the weekend. Following inquiries, police located a vehicle in Strachan Lane in Kingsford just before 9.30pm on Tuesday.
HIV cure: British patient becomes second person to beat virus
Researchers from eight countries are tracking 45 patients with cancer and HIV who have or will soon have stem cell transplants . But it in the past 18 months he was taken off the extra drugs and regular testing confirmed his viral load is now undetectable.
"Therefore, we are now treating it as being linked to the three packages being investigated by the Met in London and both investigations are being run in tandem".
Britain's senior national coordinator for counter-terrorism policing, told reporters earlier on Wednesday that the London devices were small and not meant to kill but would have required some specialist knowledge to build. Irish police are helping the Met with the investigation.
The Irish police are assisting with the investigation, a spokesperson for An Garda Siochana, Ireland's national police force, told CNN.
"We continue to pursue a number of lines of enquiry and one such line is the possibility that the packages have come from Ireland". Commander Clarke Jarrett, head of the Metropolitan Police Counter Terrorism Command, said police had not received any further reports of devices, but had "issued extensive advice to transport hubs and mail sorting companies to be vigilant".
Police received reports of the suspicious package at around 12.30pm on Thursday and an emergency response made its way to the scene.