Three people have been confirmed killed and police say around a dozen others remain missing after an explosion early on Saturday morning at a block of flats on the island of Jersey, off the coast of northern France.

Jersey emergency services said on Sunday its search and rescue operation after an explosion at an apartment building on the island was now a recovery mission, a possible indication that there were unlikely to be more survivors from the blast.

“We have three confirmed fatalities. And I think it is fair to say that we would expect to find more. Previously we have said probably in the region of a dozen,” Robin Smith, Chief Officer of the States of Jersey Police, told a news conference.

“You will understand how difficult it is to make that assessment. But that is a number we hope we don’t get to, but that is the number we are working to.”

The three-story building, located near the harbour in the island’s capital St Helier, completely collapsed in the blast.

The explosion occurred just before 0400 GMT on Saturday.

Fire services had been called to the property on Friday evening before the explosion after residents had reported the smell of gas.

Smith said the investigation would be independent and he would “rule nothing in and rule nothing out” when asked if he was treating it as a possible criminal matter.

He added that the recovery operation and the identification of bodies would take some time.

“We are not going to be here for days. We are likely to be here for weeks,” he said.