Image copyright Reuters Image caption A metal structure at the entrance to the venue collapsed in Saturday's storm

At least 14 Backstreet Boys fans have been injured after a metal structure at an outdoor concert venue collapsed in a storm in the US state of Oklahoma.

Staff were evacuating fans when rain and winds of 70-80mph (113-128 kph) knocked over the concert entrance trusses, the venue said in a statement.

All of the people injured were taken to hospital. Two have since been released.

In a tweet, the US band cancelled the show, saying: "We never want to put our fans in harm's way."

The venue hosting the concert, WinStar World Casino and Resort, said in a statement that it had asked its patrons to seek shelter from the storm at about 1700 local time (2200 GMT) on Saturday after lightning was spotted within four miles of the site.

"However, about 150 patrons who were standing in line for the Backstreet Boys concert did not heed staff's warnings," it continued.

Image copyright Getty Images Image caption The Backstreet Boys, seen here performing last month, said they would try to reschedule the concert

When the storm hit, it knocked over trusses and the entrance collapsed on top of them. The casualties were treated at the scene and transported to nearby hospitals.

One fan, who said she witnessed the incident unfold, tweeted video showing emergency vehicles at the scene:

A local reporter also tweeted images from the site:

After the incident, the Backstreet Boys said they would try to reschedule the concert.

The venue also said it would be postponed for a later date.

Band member Kevin Richardson earlier tweeted that the show had been sold out with 12,000 fans expected.

Before a decision was made about the show, fellow band member Nick Carter said safety must come first.