“We now have three deaths, I’m sorry,” Robin Smith, the states chief of Jersey police, told a news conference.
The blaze occurred just before 0400 GMT and the fire has since been extinguished. Smith said emergency services would continue to search for survivors throughout the night.
He confirmed that fire services had been called to the property on the Friday evening before the blaze after residents reported smelling gas. He did not comment on the cause of the explosion, saying it would be investigated.
Smith said a three-story building near the port in the island’s capital, St Helier, completely collapsed.
He said 20 to 30 people had been evacuated and two “running injuries” were receiving hospital treatment.
Jersey is a British Crown Dependency with a resident population of just over 100,000.