Around 2,000 people had to be evacuated from a music venue after a mysterious substance was released into the crowd, leaving several needing medical treatment.

Police were called to the Rock City club on Talbot Street in Nottingham at about 9.30pm on Friday after reports pepper spray had been released into the audience, who were gathered to watch a performance from American rapper Lil Pump.

In a statement, the venue said: “We are working closely with the police investigating the incident from the show last night where a substance believed to be pepper spray was released in the audience.

“We’d like to thank everyone attending the Lil Pump gig for co-operating with our staff so quickly as they worked to evacuate the venue after we stopped the show to ensure public safety.

“Police were on the scene quickly and paramedics treated a number of people for minor injuries.

“Live music is made to bring people together and it is incredibly sad when this type of action ruins the event for everyone.”

It is not thought anybody was seriously injured.

Nottinghamshire Police said around 20 people were seen by ambulance crews.

A spokesman said: “An investigation has been launched to establish exactly what has taken place inside the premises. CCTV and accounts from witnesses are in the process of being collated.

“It is usual for events like these to be recorded on mobile phones and cameras, and officers are appealing to anyone with footage in and around the venue at the time of the incident to contact us.

“We are treating this incident extremely seriously, however officers are not considering this to be a terror-related.”