Chicago police have deepened their investigation into an alleged sexual assault of a 15-year-old girl involving multiple people, authorities said Wednesday.

The incident — which reportedly occurred Sunday night or early Monday — was streamed on Facebook Live and viewed by dozens of people in real time, the victim’s family told police.

In a statement released Wednesday, Chicago police spokesman Anthony Guglielmi said detectives are “making good progress in the case” and “working to identify possible offenders.”

“As of now,” the statement noted, “no formal suspects have been named.”

“Superintendent Eddie Johnson also contacted the victim’s mother early Wednesday afternoon to check on the well-being of the young girl and her family,” the statement added. “He was briefed on the status of the investigation this morning and is inspired by the young girl’s courage. Additionally, State’s Attorney Kim Foxx has made victim assistance resources available to the family.”

Police told The Washington Post that the teen’s family reported her missing Sunday. Family members told WGN-TV that the teenager had gone to the store Sunday afternoon and was later spotted by loved ones on the live-feed being assaulted by several males.

“I just want her home,” her mother told the station Monday. “I just want to make sure she’s okay ’cause I know she’s probably scared and embarrassed. I just want her back home.”

Guglielmi told the Associated Press that police found out about the alleged assault after the teen’s mother intercepted Johnson on Monday afternoon as he was leaving a local precinct on the city’s West Side. The mother told the superintendent about her daughter’s disappearance and showed him screen images of the alleged assault, the AP reported.

According to AP, Guglielmi “said Johnson immediately ordered detectives to investigate and the department asked Facebook to take down the video, which it did.” He also told the AP that “Johnson was ‘visibly upset’ after he watched the video, both by its content and the fact that there were ’40 or so live viewers and no one thought to call authorities.’ ”

“What’s even more disturbing, more than the fact that they did this, there were so many people that saw this and they didn’t pick up the phone and dial 911,” Johnson told WGN-TV. “That’s just not right and we’re working on it and to bring it to a successful resolution.”

Police said the teenager was found Monday and sent to a hospital in stable condition before being reunited with her family. The incident is being investigated as a “criminal sexual assault.” Guglielmi told AP that the victim informed investigators that she knows at least one of individuals who allegedly assaulted her.

The Post typically does not identify victims of sexual violence.

Reginald King, a relative of the teenager, told the Chicago Tribune that the weekend had started out normal enough. The teen went to a basketball game Saturday and to church Sunday morning. After she disappeared Sunday, King said, he spent hours looking for the teenager. The next time he saw his relative was when a teenager told him about the assault on Facebook Live.

King told the Tribune that the video is “very, very graphic.”

“She’s pulled toward the bed,” King told the paper, referring to scenes from the video. “To have it put out there like that, publicly. It’s not right.”

King blamed the assault on a group of “thugs,” more than 35 teenagers, who have tormented local residents by carrying out violent crimes. He said adults also viewed the video, but it was a teenager who finally took action and alerted him to it.

“They are basically holding an entire community hostage,” King told the Tribune. “I literally saw adults, 60 years old, my elders, my parents’ age, cringing in fear. We were like, ‘They’re kids,’ and they were like, ‘No, they shooting people, they killing people, they robbing people.’ Over an extended period of time, they making it where kids can’t go to the store and get a snack and old people can’t come out and sit on the porch and little kids can’t play outside.”

“As a society we have to ask ourselves, how did it get to the point where young men feel like it’s a badge of honor to sexually assault a girl … to not only do this to a girl, but broadcast it for the world?” King added.

A Facebook spokesman told The Post that the company has taken down the video but declined to comment directly on the alleged assault.

“Crimes like this are hideous, and we do not allow that kind of content on Facebook,” the spokesman said. “We take our responsibility to keep people safe on Facebook very seriously and will remove videos that depict sexual assault and are shared to glorify violence.”

He said that the vast majority of Facebook Live users post responsible content online but that the company tries to interrupt streams that violate Facebook’s community standards “as quickly as possible when they’re reported to us.”

The company has teams that work “around the clock to review content that is being reported by users,” the spokesman noted.

Earlier this year, the social media giant was criticized for taking two weeks to remove a video that showed a 12-year-old girl live-streaming her suicide, according to media reports.

In July, Facebook acknowledged that although live video can be a powerful tool to document events, sharing — and allowing — videos on the platform must be done responsibly. But what has often surfaced is jarring and sometimes graphic content.

Most recently, a group of four people used Facebook Live to broadcast themselves torturing and taunting a mentally disabled teenager. In August, law enforcement officials successfully petitioned Facebook to disable the social media accounts of Korryn Gaines, who was live-streaming her armed standoff with Baltimore County police.

In October, the social media giant announced that it will begin considering the newsworthiness and public interest of difficult or graphic content before censoring it — even when it violates the site’s rules. According to its policy, Facebook does not allow self-injury or suicide.

Kristine Phillips contributed to this report. This post has been updated.