At least one person was killed and 17 others were injured in a huge explosion in a block of flats in a resort town near Barcelona, Spain, officials said on Sunday.The explosion ripped through the second floor flat of a residential building in Premia de Mar, a coastal resort town which sits northeast of the Catalan capital.The blast followed by a fire blew out windows around 8.25 a.m. (local time) in the Gran Via or main boulevard of the town 25 km northeast of Barcelona, an official said."It sounded like thunder and all of a sudden my house fell in on me," Efe news quoted a resident as saying.Over 20 families had to be evacuated due to the damage suffered by their neighbouring flats and fire services were investigating the cause of the blast, a fire official said.One of the residents was seen using a curtain to climb down from a balcony, away from the flames, as firefighters arrived.An official said that the first attenders were at the scene of the explosion within five minutes of the accident and gas supply technicians had begun to analyse what remained of the premises.It was not yet clear what caused the explosion.