The National Crime Agency (NCA) said a "sophisticated chemical method" was used and that a lab would have been needed to recover the drug.

It is believed to be the first time this method has been seen in cocaine seized in the UK.

The drugs were found among 800 sacks of charcoal on a ship that arrived into London Gateway port from Panama last week.

Armed police and NCA officers raided two farm properties in Leicestershire on Thursday after arresting two men, 50 and 31, in Coalville town centre.

They are being held on suspicion of importing class A drugs.

Two self-loading pistols and a rifle were found during a search of one of the properties.

The NCA's regional head of operations, Jacque Beer, said: "This operation has prevented a huge amount of cocaine from making it on to the streets, where it would have generated criminal profit and fuelled further violence and exploitation.

"I'm grateful to Border Force, Leicestershire Police and partners from the Leicestershire Fire & Rescue Service and East Midlands Ambulance Service for the support they have provided to our ongoing operation and investigation."