Police in Houston, Texas, have opened a criminal investigation into the deaths at the Astroworld festival on Friday.

At least eight people died and scores of people were hurt after a crowd surge on the opening night of the music event in Houston, Texas.

The victims were aged between 14 and 27. The identities of some of them are expected to be released on Sunday

Police are also investigating reports that somebody in the audience had been injecting people with drugs.

The incident began around 21:15 on Friday (02:15 GMT Saturday) when panic broke out as the crowd began to press towards the front of the stage during the rapper Travis Scott's headline set.

As the crush began causing injuries to people, panic grew and the casualties quickly overwhelmed the on-site first aiders, officials said. Some 300 people were treated for injuries such as cuts and bruises.

The police investigation into the tragedy will involve the homicide and narcotics divisions, and will review video from the scene to explore the causes of the surge and what had prevented people from being able to escape.

Several concert goers had to be revived with the anti-drug overdose medicine, including a security officer who police said appeared to have an injection mark.

"We do have a report of a security officer... that he was reaching over to restrain or grab a citizen and he felt a prick in his neck," Houston Police Chief Troy Finner said.

"When he was examined he went unconscious," he added. "He was revived and the medical staff did notice a prick that was similar to a prick that you would get if somebody is trying to inject."

In his first statement since the event on Twitter, Travis Scott thanked the police and emergency services and said he was "committed to working together with the Houston community to heal and support the families in need".

Later he posted a video message on Instagram, in which he encouraged anyone with information about the incident to contact the authorities.

Scott, whose real name is Jacques Webster, made his big breakthrough in 2013 and has since had eight nominations for Grammy Awards. He has a child with celebrity socialite Kylie Jenner, who was among the 50,000 people attending the concert.

In 2018, he pleaded guilty to a public disorder charge after he was accused of encouraging people to rush the stage at a concert in the US state of Arkansas.

According to a local newspaper, Travis Scott also paid nearly $7,000 (£5,186) to two people who said they were injured at the event.