One person has died and “around a dozen” are missing following an explosion and fire at a block of flats in Jersey after residents reported smelling gas.

Smoke billowed above the blaze in St Helier at around 4am on Saturday after the huge blast, which caused the three-storey building to collapse.

Police warned there could be more casualties after it was confirmed one person had died and two “walking wounded” were taken to hospital.

Jersey Fire and Rescue said on Saturday afternoon more pockets of fire were discovered at the scene.

Robin Smith, chief officer of States of Jersey Police, told a press conference the fire service had been called to the area the night before after residents reported smelling gas.

He told journalists: “We have a three-storey building that has completely collapsed – described from a demolition point of view as a pancake that has dropped almost straight down.

“There is also damage to a nearby building as well, another block of flats that the fire service needs to make safe. It is a pretty devastating scene, I regret to say.”

Asked how many people were missing, he said: “Given the destruction of the building it is hard to properly assess the numbers.

“We are looking in the region of around a dozen, currently.

“That number could fluctuate, but that’s the number we’re operating to.”

Daniel Hunt, a 19-year-old data administrator, who lives across the bay, told the PA news agency the explosion woke him at around 4am.

“My bedroom was shaken from the explosion with the windows rattling, which was all very unnerving,” he said.

“I went outside to take a look… I could see what looked like police and firefighters shining torches through windows of surrounding buildings. I assume as they were evacuating the surrounding area.

“The building (was) up in flames with smoke pouring out of the windows.

“To have this happen so close and so early in the morning you don’t know what to think.”

Mr Smith said the building is managed by Andium Homes, and the chief executive is “working very hard to look after” those affected.

The police chief said officers would investigate whether there was a “safety issue” regarding gas supplies.

Andium Homes, a state-owned but independent company which rents out thousands of properties on the island, said it is focusing on supporting residents at the estate.

Gas supplier Island Energy said it was working with the fire service to “understand exactly what has happened”.

Emergency services have told Jersey residents to avoid using A&E apart from in an emergency, and police have advised people to avoid the area of the blast, which has been cordoned off.

Officers said the fire has been extinguished, but emergency services are still “carrying out significant work” at the scene.

The fire service said on Twitter: “As the search at Haut du Mont has progressed, pockets of fire have been discovered.

“The site remains highly unsafe.

“A South West hazardous area response team are on site and will be joined by an urban search and rescue team from Hampshire & Isle of Wight Fire & Rescue Service.”

Residents of the flats have been moved to St Helier Town Hall, where they are being supported.

The Government of Jersey said on Twitter the Parish Church of St Helier has set up a space for people to light candles for those affected by the incident.