The agency said consignments have become more vulnerable to interceptions during lockdowns as restrictions imposed to slow the spread of Covid-19 have made it harder for organised crime groups to operate.
Aviation and shipping bans have made deliveries more difficult and heroin prices have doubled amid lockdowns in countries where drugs are sourced, such as Pakistan and Colombia, according to investigators.
“In the last four weeks, we've really seen some of those restrictions beginning to get to the organised crime groups that are moving drugs at the top of the chain,” Lawrence Gibbons, the NCA’s drugs threat head, told the BBC.
“They don't stop at times like these - and, even in a pandemic, they are still moving or attempting to move drugs.”
Three men were also arrested after cocaine with a potential street value of £3m was found in a “purpose-built hide” in a lorry which arrived at Dover on a ferry from France last month.
In an incident last week, two men were charged with allegedly breaking into the London Container Terminal in Tilbury to retrieve packages of drugs from a refrigerated container from Belize.
Senior police officers in the UK have told The Independent that the pandemic could offer an unexpected opportunity to tackle county lines drug dealing as criminals “stick out like a sore thumb” during lockdown.
Leroy Logan, a former superintendent who retired from the Metropolitan Police in 2013, said the lockdown was potentially a “blessing in disguise” for police forces looking to tackle drug crime.
“Because of the reduced footfall on the streets and the reduced traffic on the roads and on public transport, there is less anonymity for the dealers, and the higher the chance of them sticking out like a sore thumb,” Mr Logan said.
However, Lynn Owens, the NCA director-general, warned last month that street level drug dealers were trying to disguise themselves as key workers by wearing high-visibility clothing or operating from supermarket car parks to avoid police officers.
“They are having to find new ways of working and new networks,” Ms Owens said.
“Drug dealers moving illicit drugs are concerned about greater scrutiny as they recognise that with less people on the streets, they are more visible.”
Professor Simon Harding, director of the National Centre for Gang Research (NCGR) at the University of West London, said last week that gangs had been forced to adapt to coronavirus restrictions.
He said dealers were making fake NHS ID badges to move around more freely or dressing as joggers to post drugs through letterboxes.
“Vehicles are being used more often to carry out deals arranged by phone, with products thrown from windows and money chucked on the back seat to keep items clean,” Professor Harding added.
Additional reporting by PA