Sources in the MEA said apart from blocking the visa stickers, officials at all entry points have been given the serial numbers of the visas that were stolen on Sept 3 to prevent any illegal entry by their use.
They said it has also been decided that all diplomatic bags would be received by an Indian High Commission official and not by the clearing agent, as is the practice at present.
The High Commission was informed on Sept 3 that four Category 'B' diplomatic bags, including three bags that contained 6,000 visa stickers, had been stolen during transit from the Heathrow airport to India House in Aldwych, central London.
The fourth stolen bag contained stationery items, a High Commission spokesperson told PTI.
"On that day, in total 27 bags were received. Out of which, 25 bags contained 50,000 visa stickers (2000 in each bag)."
"The bags were being transported from Heathrow Airport by the clearing agent, who handles 'B' and 'C' category diplomatic bags of the High Commission since last several years", the spokesperson said.
As soon as the incident came to notice, the High Commission informed authorities in India and "suitable action" was taken to prevent any misuse of visa stickers, the official said.
A case regarding the theft of diplomatic bags was registered with the Metropolitan Police in London.
"The Metropolitan Police is investigating the case. The High Commission has also taken up the matter with the Diplomatic Protection Group."
"The existing arrangements have been reviewed and further precautionary measures are being taken," the spokesperson added.
Category 'A' bags are for materials that are considered top secret and is always transported as a hand baggage while Category 'B' contains official communications which are not secret. Category 'C' is for personal letters, newspapers and rest.