The alert came over the radio only 17 minutes into the performance of rap superstar Travis Scott, an early sign of the tragedy unfolding amid a raucous, undulating crowd at Astroworld.

“Report of individual with crush injury/breathing difficulty,” a Houston firefighter who was monitoring radio communication channels used inside the Houston music festival noted in a log at 9:18 p.m.

Reports of unconscious and trampled people — some of them in cardiac arrest — came in quick succession in the minutes that followed, according to a Houston Fire Department activity log obtained Thursday by The Washington Post.

“HPD (Houston Police Department) reports multiple people trampled, passed out at front of stage,” noted another entry at 9:30 p.m.

The show would continue another 40 minutes, until around 10:11 p.m., even after the log shows fire officials had declared a mass casualty event.

The log is a summary of communications overheard by four firefighters monitoring six radio communication channels from a mobile unit outside the venue, according to Houston Professional Fire Fighters Association President Patrick M. Lancton. Some of the channels were those being used by Houston police officers inside the venue to communicate with other fire, police and county emergency officials, Lancton said.

The document provides a detailed accounting of a festival that ended with nine dead and dozens injured on Nov. 5 in an event now under police investigation.

Autopsy reports have not yet been released. Some attendees have said they saw people crushed or trampled as the crowd estimated at 50,000 moved closer to the stage in the open air venue to see headliner Scott.

The log, first reported by USA Today, also documents the chaos at the festival earlier in the day, with reports of “dangerous crowd conditions” at a second stage, hundreds of patients treated by medical staff, and attendees overrunning security gates and scaling or toppling fences. Scores of incidents were logged, starting at 6:50 a.m. until after midnight.

The Houston Police Department maintained a regular presence at the event, deploying a drone that hovered over the crowd at the NRG Park venue, keeping tabs on the crowd size and responding to reports of injuries, the document shows. After the Astroworld event, police officials said that 528 Houston police officers and more than 750 private security guards worked at the festival.

The log recorded what the fire officials in an incident command vehicle overheard, Lancton said. The notes do not identify who is speaking during each radio transmission.

Scott, a native of Houston who rose to fame, is known for his boisterous concerts during which he has sometimes encouraged concertgoers to “rage.”

In February 2018, Scott agreed to plead guilty to disorderly conduct at a show in an outdoor amphitheater-style venue in Rogers, Ark., the previous year. Rogers police said that Scott “encouraged people to rush the stage and bypass the security protocols to ensure concert goer safety,” and that several were injured in the rush.

In December 2015, Scott also pleaded guilty to reckless conduct in Chicago after he was accused of sparking a stampede at a summer festival by urging fans to climb over barriers, court records show. A judge ordered that Scott be supervised by the court for a year, records show.

Even before the music began on Friday, there were security challenges.

In the morning, before the opening of the gates, attendees “breached the main gate and bypassed Covid testing checkpoint,” an entry at 9:23 a.m. notes. A little while later, a merchandise stand was overrun.

“Venue fences damaged, no control of participants,” an entry at 10:02 a.m. states

“Breached merchandising lines (no control over merchandise),” a fire official noted in the log three minutes later. Police later shut down the merchandise stand.

As the day progressed, the private medical company hired by event organizers, ParaDocs, saw a steady stream of injuries, treating 54 patients by 3:54 p.m., according to the log.

But that number would soon soar, as the crowds swelled in anticipation of the evening’s shows.

The Houston Police Department reported at 5:24 p.m. that it would soon launch a “private drone” over the stage, hovering at around 200 feet, the log shows. The log does not described the purpose of the drone, but it does show that police were monitoring the size of the crowd.

“HPD states crowd is growing,” the log notes at 6:48 p.m.

The log shows the determination of people hoping to see the sold-out show that also was being live-streamed on Apple Music. Some scaled or tried to crawl under perimeter fencing while others used bolt cutters in an attempt to get in, the log states. A street bordering the concert venue was teeming.

“Mob by Main Street,” an entry at 7:15 p.m. states.

At 7:35 p.m., Houston police “repositioned” 19 officers outside the stage where Scott was to perform, the log notes.

Injuries, meanwhile, began to mount.

At 8:52 p.m., less than 10 minutes before Scott was to take the stage, ParaDocs reported having treated 262 patients, according to the log.

In a statement, ParaDocs spokesman Juda Engelmayer said that the company was “prepared for the size of the venue and the expected audience with a trained team of medics and EMTs equipped for rapid emergency response.”

Engelmayer said the “vast majority of patients were treated and released,” adding that “the multiple cardiac arrests occurred during the last set in the evening.” He said the company was cooperating with authorities to properly examine “every event and incident.”

As Scott’s show started, Houston Police estimated 55,000 people were in attendance, the document shows.

At 9:28 p.m., before a rash of serious injuries, a log entry notes “This is when it all got real.” It is not clear what the note is referring to or whether it is a direct quote from a transmission, but the phrase coincided with a run of grim reports described in the log.

The multiple people who were “trampled,” as the log describes it, near the front of the stage at 9:30 p.m. were removed by “security” to the rear of the stage, the document notes.

Two minutes later police reported an “unconscious female in middle of crowd.”

One minute later, an entry states “report of multiple persons down in the crowd.”

And two minutes after that, a Houston Police radio operator said there had been five 911 calls “related to unconscious persons in crowd,” with one possibly receiving cardiopulmonary resuscitation, the log states.

By 9:52 p.m., the document shows, the fire incident commander declared the event a mass casualty incident, a trigger that doubled the number of firefighters responding to the scene.

Lancton said firefighters in the mobile command center made the decision on their own based on what they had overheard. “I believe their listening to radio traffic saved lives because critical seconds matter,” he said.

Scott’s performance ended at 10:11 p.m., 19 minutes after the log shows a mass casualty declaration triggered by the glut of medical crises.

Details about the decision-making that led to the end of the concert are not yet clear.

As the concert ended, emergency officials worked to transport the most direly injured to hospitals, the document shows.

A notation scribbled at 11:16 p.m. provided a glimpse at the toll the night had taken and the confusion that reined.

It listed the medical facilities where some of the 11 people who had suffered cardiac arrests had been transported. For five of them, the destination amid the immediate mayhem was “unknown.”