Investigators fear traffickers will use the Christmas parcel rush to smuggle class-A drugs into Britain.
In the past year suppliers have used parcels, air freight and ship containers to send heroin directly from Pakistan, the UK Border Agency (UKBA) has said.
It follows the disruption of Turkish gangs who had traditionally sent drugs by road.
In one new scam a gang posted genuine bottles of baby powder to Pakistan, where the powder was replaced with heroin and mailed back marked "return to sender".
The innocent-looking packages were collected by gang members from various domestic addresses in Hull, where residents were paid £100 a time to take delivery.
Two of the parcels were intercepted at the Mount Pleasant sorting office in London, where the bottles were found to contain heroin with a street value of more than £4m.
Jim Jarvie, of the UKBA, said: "We don't know whether the increase in heroin trafficked directly from Pakistan will be a long-term change.
"Successful law enforcement activity against criminal groups and the disruption of particular trafficking routes can reduce a threat for a time.
"The market for heroin in the UK remains and continued demand could see further changes with new criminal groups seeking access to the market using innovative methods."
One gang used a container sent to Felixstowe docks to smuggle 80kg of heroin disguised as chilli powder.
Other traffickers coated a consignment of paintings with a cocaine solution.
Agency staff use intelligence reports, technology and trends to choose which parcels to examine.
Time and resources mean they can target only a fraction of the millions of tonnes of freight and parcels that arrive each year by air and sea.
But the agency says that 65% of what it does open up contains drugs or something else illegal.
Seizures of cocaine and heroin in six months this year have already overtaken the totals for the previous year.
It includes the biggest-ever cocaine haul of 1.2 tonnes - worth £300m on the streets - found on a yacht in Southampton in August.
Source: Sky News
6:23am UK, Monday November 07, 2011