Volkswacht Bodensee - Major fire at Sweden's biggest amusement park

Police evacuated a hotel and offices connected to the Liseberg Amusement Park in central Gothenburg, and warned households in the area to remain indoors due to smoke.

According to police, 12 people sought treatment at a hospital for minor injuries.

Images showed exploding fireballs, as flames and several blasts tore up a water slide and a pall of black smoke rose over the city.

"The fire originated at one of the water attractions" outside the main building housing the water park "and then spread throughout the building", Liseberg said in a statement.

The cause of the fire was unknown, however police said the incident was being investigated as a "workplace accident".

The water park is part of an expansion of the amusement park and was set to open this year.

News agency TT said reports estimated the cost of the new water park at 1.2 billion kronor ($115 million).

NCC, the construction company building the facility, said that work had been ongoing at the site, but they did not yet know the cause of the fire.

"We have very limited information so far and want to avoid speculation," NCC spokesperson Amelie Winberg told AFP.

C.Kreuzer--VB