A veteran Chicago firefighter has been fired for brazenly and repeatedly having sex with a woman at a South Side firehouse while colleagues allegedly looked the other way.

The first of several shoes to drop in the Chicago Fire Department’s latest sex scandal targeted a firefighter assigned to Truck 24 on the Far South Side.

City Hall refused to identify the firefighter, but said his former girlfriend not only filed the complaint with the Fire Department’s Bureau of Internal Affairs that triggered the investigation, but provided all of the supporting documents needed to nail the accused firefighter.

Sources said the woman provided text messages, emails and phone records that proved “she was where she said she was” and so was the firefighter. Armed with the evidence, Internal Affairs concluded that the firehouse was used as the scene of sexual trysts — not once, but repeatedly over a long period of time.

Internal Affairs also investigated the woman’s claim that she was involved in three-way sex with the firefighter and another woman. But sources said investigators were unable to verify that any such encounters occurred on Fire Department property, sources said.

Two dozen firefighters were interviewed over the course of an investigation that dragged on for months. Sources said the now-fired firefighter filed a rebuttal to the charges that was rejected by Fire Department brass.

Two weeks ago, the Chicago Sun-Times reported that as many as a dozen firefighters were facing disciplinary action. The other firefighters, some of whom have already retired, stand accused of “varying degrees of not paying attention or looking the other way,” sources said. They either knew or should have known that the hanky-panky was going on.

Sources said those disciplinary actions are pending and suspensions are likely.

Firehouse sex is strictly off-limits. In addition, no visitors are allowed in Chicago firehouses after 10 p.m.

Jim Tracy, president of the Chicago Firefighters Union Local 2, could not be reached for comment.

Sexual harassment allegations against Hollywood movie mogul Harvey Weinstein have prompted an avalanche of allegations against men in acting, the media, the restaurant industry and politics.

Against that backdrop, the woman’s allegation about sex in a Chicago firehouse had to be taken seriously — and it was.

That’s even though it was only after the firefighter broke off the relationship that the woman chose to file a complaint.

It’s not the first time that salacious charges have been made against Chicago firefighters.

In 2000, a 27-year-old prostitute arrested for burglarizing a suburban home claimed she performed oral sex on as many as five firefighters a night at several Chicago firehouses over 11 years.

At the time, Jennifer Manzella was being held in Cook County Jail on charges that she burglarized the Elmwood Park home of a retired Chicago firefighter with whom she said she had an 11-year relationship.

She told police she was paid $25 for every sex act she performed, that the sex went on at “several” Chicago firehouses and that her roommate was performing similar acts for on-duty firefighters.

James Joyce, then the fire commissioner, threw the book at those accused of having firehouse sex with a prostitute and against firefighters who used their fire engine as a taxicab for Belmont Harbor partygoers who claimed they were too drunk to drive home.

But that wasn’t it for firehouse sex scandals.

In 2004, the Chicago Fire Department cut off Internet access at 59 firehouse computers — and ordered dozens of firefighters to undergo counseling — after determining that a computer at an O’Hare Airport station was used over a nine-month period to visit “inappropriate sites,” possibly including pornography.