Houston’s police chief said he expressed concerns about safety to Travis Scott before the rapper performed at a music festival where eight people died and hundreds more were injured in a crush of fans.

Houston Police Chief Troy Finner did not elaborate on his specific safety concerns voiced on Friday at the Astroworld festival, an event founded by Scott that was attended by some 50,000 people.

His department has launched a criminal investigation into what went wrong.

“I asked Travis Scott and his team to work with HPD for all events over the weekend and to be mindful of his team’s social media messaging on any scheduled events,” Mr Finner said in a statement tweeted by the department.

“The meeting was brief and respectful, and a chance for me to share my public safety concerns as Chief of Police.”

Representatives of Scott, who has said he was “absolutely devastated by what took place,” did not respond to an email from The Associated Press.

Houston police and fire department investigators have said they would review video taken by concert promoter Live Nation, as well as dozens of clips from people at the show that were widely shared on social media.

Investigators also planned to speak with Live Nation representatives, Scott and concertgoers.

Investigators were also interviewing witnesses and planned to examine the design of safety barriers and the use of crowd control at the event.

Live Nation said in a statement on Monday that it has provided authorities with all footage from surveillance cameras at the festival, and that it had paused removing equipment at the request of investigators who were walking the grounds.

The promoter said full refunds would be offered to all attendees.

The dead were between the ages of 14 and 27 and were from Texas, Illinois and Washington, according to Harris County authorities. They included high schoolers, an aspiring Border Patrol agent and a computer science student.

Medical examiners have still not released the causes of death, which could take several weeks, said Michele Arnold, a spokeswoman for the Harris County Institute of Forensic Sciences.

Over 300 people were treated at a field hospital on site and at least 13 people remained in hospital.

More than a dozen lawsuits had been filed as of Monday, and Live Nation announced it was delaying ticket sales for a Billy Joel concert at a different venue in Houston.

The promoter said it was assisting authorities so “the fans who attended and their families can get the answers they want and deserve”.