HOUSTON — As his music career ascended, Travis Scott developed more than the usual ties between a rap megastar and his hometown leaders. He knew the Houston police chief. His mother gave away turkeys with the mayor on Thanksgiving. He received a key to the city.
Those connections have added a layer of complication to an already freighted criminal investigation into the deaths of eight young concertgoers, who collapsed as a crowd surged toward the stage while Mr. Scott performed on Friday night during his Astroworld festival in Houston.
Houston police officers had been providing security, both on the clock and moonlighting as employees of the event organizers, according to city officials. Now the same Police Department, along with the city’s Fire Department, is in charge of the investigation.
Among the questions that touch on the role of the local police were the decisions of whether, when and how to cut off the performance by Mr. Scott, who continued the show for roughly 40 minutes after the city had declared a “mass casualty event” at the concert.
On Tuesday, Mayor Sylvester Turner met with top officials from both agencies, and his office released a collection of permits the city had issued for the festival. “No stone will be left unturned,” the mayor told reporters at an unrelated event. “How did it happen? Where were there missteps? Was the ball dropped and by whom?”
At the same time, during a meeting of county commissioners, the top county official for Houston, Lina Hidalgo, reiterated her strong interest in seeing an independent investigation of the deaths.
But any inquiry by the county could be difficult to pursue. According to a person with direct knowledge of the discussions about an independent investigation who requested anonymity to share details of a private conversation, the ability of the county to do anything has been limited by the criminal investigation announced by the city’s police chief, Troy Finner, in the immediate aftermath of the concert. Ms. Hidalgo has been considering bringing in an outside law firm or other third-party investigator.
“Judge Hidalgo is very eager to figure out what, if anything, could have prevented this tragedy from taking place by taking a thorough look at every aspect of what happened,” said Rafael Lemaitre, a spokesman for Ms. Hidalgo. He added that she wanted to see a “sober, objective analysis of what went wrong” and what could be done better in the future.
Chief Finner said on Saturday that there had been a discussion between police and fire officials, promoters and representatives of the venue, NRG Park, about the best way to end the concert early. They feared setting off “riots,” he said.
“You cannot just close when you’ve got 50,000, and over 50,000 individuals,” said Chief Finner. “I think that part was pretty good.”
On Monday, Chief Finner addressed reporting in The New York Times that he had visited the musician in his trailer before his show to express his concerns about the crowds.
“I expressed my concerns regarding public safety,” the chief, who knows Mr. Scott personally, said in a statement posted to Twitter, adding that “the meeting was brief and respectful.”
As of Tuesday, city investigators appeared to be conducting the inquiry on their own. The local branch of the F.B.I. has offered to assist, but the Houston Police Department has not requested its help, a bureau spokeswoman said. The state police have not taken a role in the inquiry.
It was not clear on Tuesday what criminal conduct the Houston police were investigating. A spokesman for the department, Victor Senties, declined to address questions.
The causes of death for the eight people killed during the concert — who range in age from 14 to 27 — have yet to be determined. The county medical examiner said it could take several more weeks.
Assigning criminal culpability can be difficult at a large-scale event where witnesses described a surging crowd that crushed and trampled people who had lost consciousness and fallen to the floor. More than 300 were injured, including a 9-year-old boy who remained in a medically induced coma in critical condition.
“The crime would have to be gross negligence rising to the level of criminal misconduct, and that is an extremely high bar,” said Steven Adelman, a lawyer and vice president at the Event Safety Alliance, a trade association focused on safety at live events.
“I don’t see any basis for criminal liability at this extremely early stage,” he said, but added a word of caution that much remained unknown.
Dozens of civil lawsuits have been filed by injured concertgoers and by the families of those whose loved ones were killed.
Tony Buzbee, a lawyer representing the family of one victim, Axel Acosta, said he would be establishing a timeline to show that the organizers and security at the festival had lost control almost from the moment the event’s gates opened on Friday.
Mr. Buzbee also questioned whether the Police Department could be counted on to conduct the investigation impartially given its officers’ role in the event. “The Houston Police Department is not going to look good coming out of this, that’s clear,” he said. “How many entities can properly investigate themselves?”
Disorder at the event had been foreseen by organizers and by the city after stampeding during the 2019 Astroworld event left at least three people injured. There was increased security this year, with a greater police presence and stronger fencing.
Still, many in the city viewed the event and Mr. Scott — born Jacques B. Webster — in a positive light. The musician spent the days leading up to this year’s festival going around Houston for community events with his charitable foundation.
The festival, named after an album by Mr. Scott, itself tapped into a sense of nostalgia among Houstonians, reviving the name of a popular amusement park where many had whiled away the day as children on the Texas Cyclone or Greezed Lightnin’ roller coasters.
“When I heard that Travis Scott was doing these kind of events, that memory came back,” said Dwight Boykins, a former city councilman who knows Mr. Scott’s father. “He was trying to bring joy and happiness back. That’s what I assumed.”
In 2018, after the first Astroworld festival, Mayor Turner proclaimed that Nov. 18 would be “Astroworld Day.”
The next year, Mr. Turner appeared onstage at Astroworld with Mr. Scott and presented him with a key to the city. The mayor said Mr. Scott’s festival had inspired him to try to create a new, permanent amusement park like the old one.
“We owe so much to this guy for keeping Houston on the map,” he said then. “This city loves you.”