Norwegian authorities have launched a probe after dozens of teenage girls were hurt in chaotic scenes at a Justin Bieber gig on Wednesday (30May12).

Officials confirmed 49 fans were injured and 14 were taken by ambulance to hospital after thousands of excited devotees descended on Oslo to see the teen idol perform a surprise concert at the Opera House.

Mayor Fabian Stang has now initiated an investigation to determine how the situation spun out of control, according to TMZ.com.

Stang says, "I have already called on the Emergency Planning Agency to examine the entire event from the planning stage to its implementation. We have to find out what went wrong and why it happened."

Local police were on the verge of declaring a state of emergency before the free show, and reached out to Bieber to help them keep the peace.

The singer took to his Twitter.com page to urge fans to remain calm, writing, "NORWAY - please listen to the police. I dont (sic) want anyone getting hurt. I want everything to go to plan but your safety must come first."

The concert went ahead as planned despite crowd control concerns - Bieber performed his hit Baby and four other songs.