NEWARK, New Jersey (AP) — The package surprised even veteran law enforcement officials used to seeing all kinds of contraband smuggled into prisons: It was a child’s coloring book, dedicated “to daddy” and mailed to a New Jersey inmate, with crayon-coloured scribbling made from a paste containing drugs.

The discovery of the book last month prompted the Cape May County sheriff to warn others in law enforcement that smuggling techniques were reaching new levels.

In Pennsylvania last month, prosecutors disrupted a prescription drug smuggling ring that was mailing narcotics into prisons concealed under postage stamps.

And in Clifton, New Jersey, police once uncovered a drug-smuggling operation under the guise of an importer bringing fresh flowers from South America in cardboard boxes that, when shredded and mixed with a solution, dissolved into liquid heroin.

Experts say even as surveillance equipment, airport scanning technology and cargo x-rays modernise, drug-smuggling techniques are keeping pace.

“It’s a question of building a better mousetrap,” said Deirdre Fedkenheuer, a spokeswoman for the New Jersey Corrections Department. “Somebody’s going to always try and think of a new way.”

It’s been more than a decade since sending food to prisoners was prohibited, but today, drugs, weapons and cell phones still find their way behind bars, according to Fedkenheuer. New Jersey’s prison system has added dogs trained not only to sniff drugs, but to detect the odor of cell phones as well, which are banned.

It’s not only prison smuggling that gets creative, according to United States Customs officials. Smugglers try all sorts of techniques to bring contraband into the country by air, sea and land.

Smuggling drugs into the US has been going on as long as there’s been a market for illegal substances, according to John Saleh, a Customs and Border Protection officer based in New York.

“The drug industry, drug trafficking, is a billion-dollar or trillion-dollar business,” Saleh said. “It’s a business that makes money, so they’re very cunning in their ways of masking something, or smuggling something in so they can make a profit.”

In the past two months alone, inventory confiscated at New York-area airports and ports included opium concealed in porcelain cat figurines, cocaine in bags of freeze-dried coffee, drugs built into the railings of a suitcase, sewn into pants, moulded into sneakers, concealed in clothing hangers or packed into the console of a Nintendo Wii video game system.

“You name it, we’ve probably seen it,” Saleh said. Drugs have been hidden in electrical cords, in a computer mouse, a child’s Mr Potato Head doll, baby diapers, drug-soaked clothing, toothpaste, cosmetics, fruit that is expertly sliced, gutted, filled with drugs and resealed to look untouched, or in live animals — such as puppies — and of course, in people.

Even for customs officials like Saleh, who think they’ve seen it all, every once in a while, a smuggler surfaces whose level of craftsmanship has to be admired. Saleh said one of the most shocking finds was a cache of cocaine that had been sculpted into the size and shape of individual black-eyed peas, each one painstakingly hand-painted with tiny black markings to blend in with a bag of real beans.

Customs enforcement agents use a multi-layered approach, according to Saleh, to detect smugglers or illicit goods; a mix of technology, intelligence techniques and officers on the ground.

Kevin Donohue, a deputy chief officer with US Customs at Newark Liberty Airport, says that in addition to drug and agricultural product-sniffing dogs, scanning technology and luggage searches, the most effective way to catch smugglers is by being able to read people and detect scenarios that may seem slightly off. A young woman with small feet, carrying size 14 sneakers in her luggage. A beat-up, older-model suitcase with shiny new screws in its base. Travellers who watch the carousel a bit too anxiously for their bag. A person carrying a huge tub of peanut butter from a country that doesn’t produce it. A hard-shell suitcase coming from a country where nearly everyone carries soft-sided luggage. They are all real scenarios in which drugs or illegal contraband have been found at the airport, Donohue said.

“You pretty much become an expert in the suitcase,” Donohue said. “Rivets, bolts, the way it’s made, the weight of every kind of suitcase.”

Airports tend to have smaller-scale drug smuggling, although Donohue said there are agents on his force who are also trained airplane mechanics and search aircraft for hollow contraband cavities.

That leaves traffickers hoping to move larger quantities to find other methods.

In 2010, a truckload of white sea bass headed into San Diego from Tijuana, Mexico, was found to contain 708 pounds (320 kilogrammes) of marijuana wrapped in 29 packages and stowed beneath the fish and a layer of ice.

In Dallas, a man pulled over for a traffic violation was found to be transporting a casket carrying 100 pounds of marijuana instead of a body.

A corrections officer in Arkansas was arrested in 2008 for making frequent takeout food deliveries to the county jail and was caught sneaking syringes inside tacos and marijuana under chilli.

Smugglers also use a wide variety of methods to get drugs across borders.

Soldiers in Colombia seized a fully submersible drug-smuggling submarine in February, capable of reaching the coast of Mexico. Last July, another fully submersible ‘narco-sub’ was seized just across the border by authorities in neighbouring Ecuador.

And this past January, US and Mexican law enforcement officials discovered drug traffickers in Mexico using an ancient technology — a giant catapult — to hurl marijuana across the US border into Arizona.

Those on the front lines of stopping contraband, like Customs officials, are rarely ever surprised.

“There really are no new ways,” Saleh said. “If you can imagine it, they’ve probably done it.”