Britain's National Crime Squad said its officers, assisted by the Customs and Excise department, stumbled across the bonds during a drug raid on a house in London in July.
"We are still conducting inquiries as to whether the bonds are genuine or not," a spokeswoman said on condition of anonymity.
If they are, the raid could be one of the most lucrative ever in the battle against drugs.
The seized assets include automobiles, houses and furniture, she said.
During the July and August raids on house in north London and the nearby county of Essex, officers also found 55,000 ecstasy tablets, 33 pounds of amphetamine powder, and small amounts of ecstasy powder and cocaine, the spokeswoman said.
Nine men were arrested and charged with conspiracy to import cocaine and conspiracy to supply ecstasy. They appeared in court this summer.
The raids led authorities to privately share information about the cartel with officials in Colombia, and 21 pounds of cocaine was then found by police in Ecuador. Two people, believed to be Colombians, were arrested by Colombian authorities a week ago.
"During our investigation, we came across a lot of things that were linked to Colombia," the National Crime Squad spokeswoman said. "We contacted the Colombians and started working together and started to exchange intelligence."
In Britain, three other men and a woman were arrested in addition to the nine charged, but all four were released on police bail.
The nine facing drugs charges are all from north London or Essex, but one has a house in Colombia, the spokeswoman said.
They appeared in a court in Aldershot, Hampshire, on July 20 and Aug. 9, and are due to appear in Winchester Crown Court in mid-November, she said.
The spokeswoman said the first raid in England was not made public to avoid jeopardizing the second operation in August. Nothing was made public at that point either to enable Colombian authorities to continue their investigations, she said.
Guillermo Anibal Ortega, director of the Colombia's attorney general's office investigative unit in Bogota, said: "This is a very important victory because it represents the most overwhelming blow against drug trafficking and money laundering."
The ring allegedly sent drugs from Colombia to Europe via countries like Ecuador and Mexico, he said.
Ortega declined to identify the drug cartel most affected by the raids because authorities plan to continue making arrests in other European countries.
New of the large-scale drug and money bust only emerged in London on Thursday night after Colombian authorities announced details of the raids in Bogota.
The ring allegedly sent drugs from Colombia to Europe via countries such as Ecuador and Mexico, Ortega said. He declined to identify the drug cartel most affected by the operations, saying authorities plan to continue making arrests in other European countries.
The Colombian navy and attorney general's office worked with British customs officials and Britain's National Crime Squad to gather intelligence over the last six months, Ortega said.