A young man who was stabbed at a festival in Queen Elizabeth Olympic Park at the weekend is said to be in a critical condition in hospital.

Newham detectives launched an investigation after the double stabbing which took place on Sunday night at around 9pm at the Yahoo! Wireless Festival.

Rapper Jay-Z was performing at the three-day festival at which Justin Timberlake was a headline act.

The men were taken to separate east London hospitals with stab wounds; police initially reported a victim in his 20s was stable but his condition has since worsened. The other victim, also thought to be in his 20s, has been discharged from hospital. It is believed that a screwdriver was used.

A spokeswoman for the festival organisers, Live Nation, said: “Live Nation is deeply saddened by this isolated incident. Aside from this Wireless Festival was a hugely successful event that took place over three days and was enjoyed by 170,000 music fans. Safety is paramount at Live Nation events and we are assisting the Metropolitan Police with their enquiries.”

Police believe the two men were with a group which became involved in an argument with a group of up to ten black men near the front of the stage before the stabbing incident.

A spokesman for the London Legacy Development Corporation said: “This is a dreadful but isolated incident in a three-day event in which more than 170,000 people have enjoyed a weekend of great music. Over the last three weeks more than 300,000 people have come to enjoy concerts on the Park.”

He said the corporation worked closely with event organisers and the emergency services to ensure such events take place without incident.

He said: “We have plenty of other events over the next few weeks and throughout August. They will be wonderful events and we will plan very carefully for these events because people’s safety is of paramount importance for us.”

In light of the warm weather he said the venue had relaxed its rules on how much water people can take with them. Free water and sun screen have also been made available to visitors.