(Revises death toll; adds detail, witness accounts) By Felix Ordonez PALENCIA, Spain, May 1 (Reuters) - A five-storey apartment block in the Spanish city of Palencia collapsed after an explosion caused by a suspected gas leak on Tuesday, killing at least three people, emergency services said. At least 25 were injured by the morning blast near Palencia's cathedral, a spokesman for the emergency services said. One seriously injured six-year-old girl was airlifted to hospital in nearby Salamanca. Media reports said at least five had died, and the city's mayor was quoted as saying others were still trapped in the rubble. The emergency services spokesman said the death toll was likely to rise. "There are probably going to be more dead, but at the moment there are three identified," he said. The explosion's shockwave blew out windows in a 200-metre (yard) radius. "There was a huge explosion. It has blown out the shutters and the windows. It was horrible," one woman told state television. Palencia is 240km (150 miles) north of Madrid. Television news showed rescue workers crawling over what remained of the totally flattened 10-apartment building, carrying out bodies on stretchers. Authorities said they did not know how many people were at home when the blast ripped through apartments at 5:47 a.m. (0347 GMT). Spain is celebrating the May Day public holiday on Tuesday which meant many people may have been away from home. "We can't rule out that there could still be people alive because in ruins like this there may be pockets in which people can survive," a rescue sniffer dog handler told state radio. Emergency services and experts from utility Gas Natural are investigating whether a gas leak destroyed the 30- or 40-year-old building, the spokesman said. (Additional reporting by Jason Webb and Ben Harding)
