Mexico’s ruthless drug cartels are using helpless children as decoys to smuggle their members into the U.S. — courtesy of the Biden administration’s relaxed immigration policies, law enforcement told The New York Post.

The drug thugs are already making a killing off the border crisis, jacking up their fees to smuggle the growing flood of people into the country — and now "making more money on humans than they are on the drug side," said Hidalgo County Sheriff J.E. Guerra from the front lines of the U.S. immigration battle in Texas.

But the cartels also are further exploiting the disastrous situation by splitting up kids from their wannabe immigrant parents, then having members pose as the children’s relatives to cross the border, Guerra said.

"So now with the family units coming across, you might have a mother come in, say, a mother with three children," Guerra said.

"Well, the cartels say, ‘You can cross with one child, we’re going to take two children. And we’re going to use those two children to smuggle two others and pretend that those are family units.’"

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Young criminals will pose as struggling wannabe migrants, too, to get to the U.S. to help fuel their bosses’ drug trade, the sheriff said.

"We also have individuals that might be 21, 22, and they pass themselves off as 16, 17 years old and say, ‘Hey, we’re an unaccompanied minor.’ And they might give false name. And they might have a criminal record in their countries,’’ Guerra said.

But some of the youthful drug criminals have made a key mistake trying to disguise themselves, he said.

"The cartel guy, he’ll take off his shirt and blend in with the rest of them. … [But] he doesn’t have muddy shoes, he’s got cleaner clothes, he doesn’t smell’’ — that’s a clue for authorities that he may not be on the up and up, the sheriff said.

The U.S. is struggling under an avalanche of migrants — particularly unaccompanied kids — trying to cross its Mexico border since President Biden reversed several key Trump administration policies.

But while the situation may be bad news for many, it’s a "boom" financially for the drug trade not only because cartels are smuggling in members, but considering how desperate the increasing number of migrants are to cross the border, Guerra said.

"Right now, it’s a boom. It’s a boom for them — it’s huge," the sheriff said, referring to the cartels and current U.S. policies.

"Anywhere from $1,000 to $1,500 for every single body, and you put the number to it, and you figure out how much money they’re making," he said of the cartels and what they charge immigrants to help them illegally cross the border.

"There’s no way you’re going to get across without paying. And [the cartels are] making a killing right now."

The sheriff said the desperation of families leads to all sorts of other tragic situations, too.

"So if you can’t afford it, and you have that little 15-, 16-year-old child with you, well, guess what?" he said.

"Well, you’re gonna go to Houston. And that little girl is gonna go to work in sex-trafficking and that little girl is going to pay off all your debt. That’s happening," Guerra said.

Pedophiles and other convicted felons — including those already booted at least once from the U.S. — are more than pleased about the chaotic situation, too, because they believe they are getting another chance at a bite at the illegal-immigration apple thanks to it, the sheriff said.

This situation only helps the cartels further because they can charge a premium to smuggle in such people, Guerra said.

"The previous convicted felons and the pedophiles and the people that have been convicted of sexual assault that have been deported — you’ll see those coming across in droves," Guerra predicted. "And the cartels know that, so they charge them a lot more money."

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Meanwhile, in terms of an increased drug flow across the border, the sheriff said he’s not concerned for his community — he’s more worried about further north.

"It doesn’t pose a security threat for us. … The drugs don’t stay in my community. They don’t stay here. They go up north. And we’re trying to stop it here," Guerra said.

"What you’re seeing today is methamphetamine. heroin. You’re still seeing cocaine. But you’re seeing fentanyl. That’s killing people. Because opioids are just poison."