Child-welfare officials are investigating Anthony Weiner in the wake of The Post’s exclusive report that he sent a lewd selfie that showed his young son lying in bed next to him, sources said Wednesday.

The probe of Weiner was launched by the Administration for Children’s Services over his handling of 4-year-old son Jordan, a city government source told The Post.

Agency protocol requires a home visit within 48 hours, and ACS showed up at Weiner and estranged wife Huma Abedin’s Union Square apartment building on Tuesday, a worker there confirmed.

Such initial visits are meant to ensure that a possibly at-risk child has a room to sleep in and food to eat, the government source said.

Exclusive video shot by The Post showed Weiner leaving his building alone around 6 a.m. Tuesday, and it was unclear if ACS gained access to his apartment.

Weiner said early Wednesday that he had not been visited or interviewed by ACS.

He didn’t return a request for comment later in the day, after The Post confirmed the probe arising from his latest — and gravest — online indiscretion.

Weiner, 51, quit Congress over a sexting scandal in 2011, then saw a 2013 comeback bid for mayor collapse when he was revealed to have sent a woman a photo of his privates using the pseudonym “Carlos Danger.”

A gallery of photos from Anthony Weiner’s latest sexting scandal:

State Sen. Ruben Diaz Sr. (D-Bronx) — who on Monday publicly demanded an ACS investigation of Weiner — called confirmation of the probe “good news.”

“Praise the Lord. Every child should be protected,” said Diaz, who is also founder and pastor of the evangelical Christian Community Neighborhood Church in The Bronx.

Diaz said he tried to personally call ACS Commissioner Gladys Carrion to ensure an investigation, but got blown off by her staff.

Diaz said Wednesday’s Post front-page story revealing that Weiner boasted of using his son as a “chick magnet” provided even more evidence that an investigation was warranted.

“The baby is being used for sex. Who uses a baby to get girls? That baby is being abused,” Diaz said.

The Bronx pol also expressed concern that Weiner’s high-level political ties — Abedin is a longtime, trusted aide to Democratic presidential nominee Hillary Clinton — could affect the outcome.

“Weiner has powerful friends. He has a powerful wife. He’s not a John Doe out in the street,” he said.

Meanwhile, Catholic League President Bill Donohue filed a report of suspected child abuse with the state Office of Children and Family Services, citing the two Post reports.

“It would appear that Mr. Weiner’s sexual exploitation of his child meets the definition of child sexual abuse . . . Please investigate this matter.”

Donohue’s complaint lists both Weiner and Abedin, who declined comment.

Abedin, 41, announced she was separating from Weiner on Monday morning, hours after The Post published her hubby’s disturbing crotch shot featuring their son.

Weiner should have learned his lesson years ago:

Additional reporting by Carl Campanile