At least six people have been injured after a building in Vienna partially collapsed following a reported explosion, police in Austria have said.

Spokeswoman Adina Mircioane says rescuers are trying to reach one injured person inside the residential building in the city’s 15th district. Five other people are being treated for minor injuries.

Ms Mircioane says other people may still be trapped inside the building, whose top two floors collapsed shortly after 10am.

Austrian public broadcaster ORF carried a photo on its website showing a cloud of dust enveloping a street.

“We are also bringing in sniffer dogs to search for other people who might be trapped inside,” Ms Mircioane said, adding that the cause of the explosion was not yet known. Witnesses said they heard a dull thud before the top two floors of the building collapsed, raining debris onto the street.

“There was a cloud of dust, and lots of people screaming and running,” said Ted Knops, a 32-year-old local resident. “It was like a science-fiction movie when something comes bursting through the wall.”