Exclusive: Behind the scenes with DEA agents trying to stop the flow of heroin into NYC

NEW YORK (WABC) -- 30 percent of all the heroin smuggled into the United States gets into the country though New York borders.

We flew with the DEA to see the drug pipeline routes into the city, going behind the scenes with the crime fighters who are racing to close down these routes because people are dying at alarming rates.

It's enough to kill an entire herd of elephants. Fentanyl, 100 times more powerful than morphine.

Now routinely mixed with heroin, and flooding the streets of New York.

"Heroin is coming to New York and the U.S. more than ever," said James Hunt, Special Agent in Charge, who runs the DEA's New York operation.

"You get a real sense of the scope of the problem when you're 1,000 feet above it," we said as we joined Hunt in a helicopter.

"You really can see how many different ways there are to get into the city. It makes a tough road for law enforcement," said Hunt.

Most of the heroin is smuggled in by the truckload, packed into tractor-trailers and driven up from Mexico, over the Verrazzano and into Brooklyn, over the GW and into the Bronx.

"The Mexican cartels have been flooding the U.S. market with heroin, pushing it here. They want to create more addicts. That's their business plan, and it's an evil plan," said Hunt.

Just last month, agents arrested two men after they found over 65 pounds of heroin hidden in the axle of their tractor-trailer.

"If it were heroin alone it would be bad enough, but fentanyl is a big part of the problem," we said to Jonathan Wilson, Associate Special Agent in Charge for the New York DEA.

"Fentanyl is a huge problem," he said. "The purity is much too high for the individual user", he said. "And this explains the spike in overdoses and deaths?", we asked. "I believe so. yeah," said Wilson.

With overdoses and deaths at an all-time high, the DEA's Manhattan lab is overwhelmed by the sheer volume of heroin seizures.

"What does that say to you?", we asked DEA Northeast Lab Director Thomas Blackwell.

"That we're looking at a serious crisis, here," he said. "Probably of the 27 chemists I have on staff, well over half to three quarters are working on heroin or fentanyl-related cases."

'It's a big problem, but you've had your share of successes," we said to James Hunt.

"We catch the biggest bad guys, we make big cases against these criminal groups, but it's not something we can stop alone," said Hunt.

One third of all the heroin seized by the DEA is seized in New York, a number that doubles every year.