LONDON, March 5 -- The London Metropolitan Police Counter Terrorism Command has launched an investigation after three suspicious explosive packages were found at buildings in London on Tuesday.

The packages -- all A4-sized white postal bags containing yellow Jiffy bags -- have been assessed by specialist officers to be small improvised explosive devices.

"These devices, at this early stage of the investigation, appear capable of igniting an initially small fire when opened," the Scotland Yard said in a statement.

The Met Police Counter Terrorism Command said they are treating the incidents as a linked series and is keeping an open mind regarding motives.

According to the Met Police, at approximately 9:55 am they received a report of a suspicious package at The Compass Center, Nelson Road, Hounslow. The package was opened by staff at the building, causing the device to initiate. This resulted in part of the package burning.

No one was injured. The building was evacuated as a precaution. Specialist officers attended and made the device safe. The building remains closed as enquiries continue. The building is not based at Heathrow Airport, and flights have not been affected by this incident.

At approximately 11:40 am, British Transport Police were called to reports of a suspicious package in the post room at Waterloo Station. The package was not opened. Specialist officers attended and made the device safe. No one was injured.

The station was not evacuated however cordons are in place at a small area outside the station on Cab Road. Train services are continuing to operate as normal.

At approximately 12:10 pm, police were called to a report of a suspicious package at offices at City Aviation House, Royal Docks, Newham. Staff was evacuated from the building as a precaution. The package was not opened and no one was injured. Specialist officers attended and made safe the device. The building has been reopened.

As a precaution, DLR services to London City Airport were suspended but are now fully operational. Flights to and from the airport have not been affected.

The Met Police has issued advice to transport hubs across London to be vigilant for and report suspicious packages to police.

British Transport Police Assistant Chief Constable Sean O'Callaghan said they will have a number of specially trained officers on duty to keep commuters safe and reassured.

"Officers will be highly visible on station concourses, on board trains as well as the London Underground network. If you have any concerns, please speak with us or indeed a member or rail staff," he said.