The parcel company at the centre of a UK bomb incident last year has been barred by the Government from screening air cargo at some UK sites for security reasons, it was announced today.
Confirmation of the UPS situation was made by the Department for Transport (DfT).
The DfT said: "The safety of the travelling public is paramount and our security regime is kept under constant review.
"We can confirm that, following careful consideration, the department has restricted the number of sites in the UK at which UPS Ltd are permitted to screen air cargo until it has satisfied current security requirements. For obvious security reasons we will not comment on the details."
New security measures affecting the transfer of cargo through the UK came into force at the beginning of November last year following the discovery at East Midlands airport of an explosive device hidden in a printer cartridge on a UPS aircraft.
A device was also found on an aircraft in Dubai.
The bomb at East Midlands was removed by Leicestershire Police officers shortly after 3.30am on October 29 after a tip-off from Saudi intelligence.
It had travelled through a UPS hub at Germany's Cologne Airport before being detected in the UK after the tip-off.
It later emerged that the explosives discovered at East Midlands and in Dubai were at least 50 times more potent than would be needed to blow a hole in an aircraft fuselage.
After last year's incidents, Home Secretary Theresa May said the East Midlands and Dubai bombs originated in Yemen and were believed to be the work of al Qaida.
She announced that all flights containing unaccompanied freight from Somalia would be suspended. Unaccompanied air freight from Yemen had already been suspended earlier last year.
Also, ink cartridges of more than 500g were banned from hand baggage on flights departing from the UK and also on cargo flights unless they originated from a regular shipper with security arrangements approved by the DfT.
A UPS spokesman told the BBC website: "As part of a scheduled review by the DfT of UPS procedures and employment documentation related to security, the DfT identified areas of concern that UPS now is working to address.
"Some facilities have been temporarily taken offline, which in some cases has led to delays in the movement of packages. UPS has activated contingency plans, communicated with customers and expects service levels to return to normal early next week."
He went on: "The DfT reviews have been helpful, educating UPS on the expectations of DfT auditors.
"UPS continues to assess the operation of its UK network and, in co-operation with the DfT, may refine it to ensure an even more efficient level of service to its customers."
Later, a UPS spokeswoman said: "Security is a shared responsibility requiring a partnership between private enterprise and governmental authorities around the world.
"UPS routinely works with all the appropriate agencies and authorities around the world, including the UK's Department for Transport, to ensure the safety of its network."
She went on: "A Dft scheduled review identified areas of concern UPS is working to address. As a result, some facilities in the UK have been temporarily taken offline, which in some cases has led to delays in the movement of packages.
"UPS has activated contingency plans, communicated with customers and expects service levels to return to normal early next week.
"In cooperation with the DfT, UPS continues to assess the operation of its UK network to ensure full compliance with EU and UK security requirements, leading to a higher level of service to its customers.
"We cannot reveal any specific details about our security procedures as this would be counter-productive to their effectiveness.
"We continue to work with all agencies around the world to maintain and enhance security and to balance necessary protections with the free flow of commerce, just as we have always done."