Firefighters and army experts on Friday were calculating the risks of entering a residential block that was destroyed by fire in the eastern Spanish city of Valencia, killing four people and leaving 14 missing.

Valencia Mayor Maria Jose Catala said that both the danger of the 14-story building collapsing and the continuing intense heat from the fire were preventing emergency workers from getting in to search for possible survivors.

Firefighters continued to hose down parts of the gutted building some 15 hours after the blaze started. Catala said six injured people remain in city hospitals, four of them firefighters.

It was not immediately made known how many people were in the building at the time, but dozens are believed to have lost their homes and belongings. Residents of the building were given accommodation in hotels or in the homes of relatives or neighbours, authorities said.

Firefighters rushed to the scene on the outskirts of the city centre on Thursday evening as flames burst from windows. Firefighters used a crane to lift two residents from one of the balconies.

The fire started in one part of the complex and spread to an adjacent building. Some 90 soldiers from Spain's Military Emergency Unit and 40 firefighting trucks also were deployed.

The cause of the fire was still not known early Friday. Catala said it was too early to comment on news reports that suggested it might have spread rapidly owing to materials used in the building's structure. The building was said to have been built some 15 years ago.

The fire sent clouds of black smoke billowing skyward that could be seen from afar. Spain's weather agency, Aemet, reported winds of up to 60 kph at the time.