At least 18 people were injured, three critically, when a wooden staircase leading from a bridge to a canal collapsed during a musical concert in the central Dutch city of Utrecht, police said.

Police spokeswoman Mieke Kort said three people were in a critical condition, five more were seriously injured, and about 10 had minor injuries.

Several people were thrown into the water and Kort said police divers searched the canal for more possible victims, but found nobody.

CountryWatch: Netherlands

The victims had been crowded onto an old wooden staircase leading from a bridge down to the side of the canal in Utrecht's historic city center, and were watching a salsa concert when the structure gave way.

"It was terrible, I saw people covered with blood," said Robert Smit, who was in a boat watching the concert with his girlfriend when the stairs gave way. "There were many people standing on the stairs, jumping and dancing to the music and then the whole structure suddenly collapsed."

An AP photographer at the scene said he saw three injured people being carried away from the canal on stretchers and one victim lying in a boat being treated by paramedics.

The accident happened at the end of an event called the Musical Boat Parade, which drew thousands of fans Sunday to watch different musical acts performing on floating stages on the canals of central Utrecht.

Rinda den Besten, a member of the city council, said an investigation would be launched to determine the cause of the collapse.