A stampede of fans surging toward the stage during rap star Travis Scott's Astroworld music festival in Houston killed at least eight people and injured dozens more as panic rippled through the crowd of largely young concertgoers, officials said on Saturday.
City Police Chief Troy Finner said his department has opened a criminal investigation by homicide and narcotics detectives following unconfirmed reports that someone in the audience "was injecting other people with drugs.
Finner said that among the "narratives" under review by police were reports suggesting "some individual was injecting other people with drugs."
One report involved a security officer "who felt a prick in his neck" as he was trying to restrain or grab someone and then fell unconscious, only to be revived with a dose of the opioid antidote naloxone, Finner said, citing an account from medical personnel who treated the officer.
Finner said the medical staff also noticed what appeared to be a needle mark on the officer's neck.
It was not clear whether authorities suspected such an episode played a role in the crowd surge, but Finner said, "we're going to get down to the bottom of it."
Police were awaiting autopsies to determine the causes of death, but said some victims were trampled.
Finner said police had 528 officers assigned to the festival on Friday, along with 755 private security personnel.
Throughout the day, 25 arrests were made - one each for marijuana possession and public intoxication and the rest for trespassing, Finner said.