Investigators are working to determine how eight people died in a crush of fans at a Houston music festival, as concertgoers recounted the horror and confusion of being trapped in the crowd and mourned the dead.

Authorities plan to use videos, witness interviews and a review of concert procedures to figure out what went wrong on Friday night during a performance by rapper Travis Scott.

The tragedy unfolded when the crowd rushed the stage, squeezing people so tightly they could not breathe.

Billy Nasser, 24, who had travelled from Indianapolis to attend the concert, said about 15 minutes into Scott’s set, things got “really crazy” and people began crushing one another. He said he “was picking people up and trying to drag them out”.

Nasser said he found one concertgoer on the ground, adding: “I picked him up. People were stepping on him. People were like stomping, and I picked his head up and I looked at his eyes, and his eyes were just white, rolled back to the back of his head.”

Over the weekend, a makeshift memorial of flowers, candles, condolence notes and T-shirts took shape at NRG Park.

Michael Suarez, 26, went to the growing memorial after attending the concert.

”It’s very devastating. No one wants to see or hear people dying at a festival,” he said. “We were here to have a good time — a great time — and it’s devastating to hear someone lost their lives.”

The dead, according to friends and family members, included a 14-year-old high school student, a 16-year-old girl who loved dancing, and a 21-year-old engineering student at the University of Dayton. The youngest was 14 and the oldest was 27.

Thirteen people remained in hospital on Sunday, but their conditions were not disclosed. More than 300 were treated at a field hospital at the concert.

City officials said they were in the early stages of investigating what caused the chaos at the sold-out Astroworld festival, an event founded by Scott, which had about 50,000 in attendance.

Authorities said that among other things, they will look at how the area around the stage was designed.

Steven Adelman, vice president of the industry group Event Safety Alliance, which was formed after the collapse of a stage at the Indiana State Fair in 2011 killed seven people, helped write industry guidelines widely used today.

He said investigators will examine the design of the safety barriers and whether they correctly directed crowds or contributed to the crush of spectators. He said authorities will look at whether something incited the crowd besides Scott taking the stage.

Mr Adelman said another question is whether there were enough security staff there, noting there is a nationwide shortage of people willing to take low-wage, part-time security gigs.

“Security obviously was unable to stop people. Optically, that’s really bad-looking,” he said. “But as for what it tells us, it’s too early to say.”

Houston police and fire department officials said their investigation will include reviewing video taken by concert promoter Live Nation, as well as dozens of clips from people at the show.

Officials also planned to review the event’s security plan and permits issued to organisers to see whether they were properly followed during the event.

In addition, investigators planned to speak with Live Nation representatives, Scott and people who were at the concert.

On video posted to social media, Scott could be seen stopping the concert at one point and asking for aid for someone in the audience: “Security, somebody help real quick.”

In a tweet posted on Saturday, he said he was “absolutely devastated by what took place”, and pledged to work “together with the Houston community to heal and support the families in need”.