A gas break is likely to blame.
An explosion in a Prague building this morning injured about 35 people and forced the evacuation of several surrounding buildings. There have been reports that officials believe a few people may still be missing. Right now, the explosion is being attributed to a gas explosion.
The Associated Press writes:
The blast shattered windows in the scenic area of charming streets and postcard-pretty buildings, sending glass flying. Authorities closed a wide area around the site and some tourists were stranded on street corners with baggage-loaded trolleys, unable to get into their hotels.
CNN reports that over 230 people were evacuated from the area in central Prague. Nearby buildings for Charles University and the Film and TV School of Academy of Performing Arts in Prague were also evacuated.
The Associated Press posted this footage of the aftermath (note that they have since revised their reported injury count).
RAW VIDEO: Explosion in Prague damages building and injures up to 40 people, others may be trapped: apne.ws/16bBFM9 -KM— The Associated Press (@AP) April 29, 2013
Photos from Reuters of the streets today show bloodied faces and crowds of onlookers.