HOUSTON: At least two investigations, one of them criminal, were underway on Sunday into the deadly stampede during rap star Travis Scott's Astroworld music festival that killed at least eight people and injured dozens in Houston.

Officials in Houston said autopsies on Friday's victims were being performed as soon as possible so their bodies could be returned to family members, with the identities of some of the dead expected to be released on Sunday.

The dead were young, Houston Mayor Sylvester Turner told reporters on Saturday: two were aged 14 and 16, two were 21, another two were 23, with a seventh aged 27.

An eight victim has yet to be identified, he added.

Harris County Judge Lina Hildago called for an "objective, independent" investigation into the tragedy, as she spoke about the rap festival being attended by 50,000 fans when the stampede took place.

"Perhaps the plans were inadequate. Perhaps the plans were good but they weren't followed," Hildago said. "The families of those who died, everybody affected, deserves answers."

In a 90-second video released on Twitter on Saturday, Scott said that, while on stage, "I could just not imagine the severity of the situation." He described himself as "absolutely devastated" by the incident.