Five men have been arrested after Felixstowe Border Force officers thwarted a drug smuggling plot worth millions of pounds.

Officers discovered a huge haul of heroin, weighing 46 kilos - around 101lbs, after it arrived at Felixstowe docks following its attempted importation from Pakistan.

The Class A drugs were discovered in a shipping container which had industrial machinery inside it.

The heroin was concealed within the machinery.

The seizure was made on September 1 and referred to the National Crime Agency’s (NCA) Border Policing Command.

Details of the find were unable to be released until today due to the ongoing NCA investigation.

At present the purity of the drugs has yet to be established so no accurate figure can be put on the street value.

However, at a trial in 2012 13 kilos of pure heroin was said to be worth £1.5million. This would mean the drugs found at Felixstowe could have a street value of around £5million if they were pure.

All of those arrested by the NCA were detained on suspicion of importing a Class A drug.

A 56-year-old from Inverness, three men aged 55, 52, and 21, from the Hinckley area of Leicestershire, and a 52-year-old man from Chelmsley Wood, Birmingham, were all questioned by investigators before being released on bail pending further enquiries.

Border Force regional director Phillip Holliday said: “Border Force officers have prevented a substantial quantity of dangerous class A drugs from ending up on the streets of the UK and put a serious dent in the profits of the international criminal networks involved in this type of smuggling.

“The purity of the drugs is still being tested and a precise value of the haul is therefore yet to be established, but it will certainly run to millions of pounds.

“Working with our colleagues at the NCA we are determined to do all we can to stop drug traffickers. Those convicted of drug importation offences face considerable prison sentences.”

Criminal investigations launched as a result of Border Force seizures of prohibited items and goods are undertaken by officers from the NCA.

The NCA is leading the UK’s fight to cut serious and organised crime, including child exploitation, drug and people smuggling, illegal immigration and fraud and cyber crime.

Anyone with information about activity they suspect may be linked to smuggling should call the Border Force hotline on 0800 59 5000.