Image copyright Getty Images Image caption Fans gathered outside Prince's estate to pay their respects following his death

The family members of pop singer Prince have begun the process of dividing up the American singer's sizeable assets.

Prince Rogers Nelson left no known will and his assets are estimated to be worth about $100m (£68m).

The singer died at his Paisley Park compound outside Minneapolis, Minnesota, on 21 April.

His sister, Tyka Nelson, and half-siblings are the apparent heirs to his estate, authorities have said.

Ms Nelson and and Prince's half-sibling Alfred Jackson attended a hearing on Monday at the Carver County courthouse in Minnesota, where lawyers began surveying the singer's estate.

If no will is found, the state will determine how the money is divided up.

During the short hearing, Judge Kevin Eide formally appointed Bremer Trust National Association as the special administration to oversee Prince's probate case.

One attorney said there was an "ongoing search" for a will.

Image copyright AP Image caption Prince's sister Tyka Nelson said her brother left no known will

Investigators are still determining how the singer, songwriter and producer died.

Prescription painkillers were in the singer's possession when he died. But it is unclear what role, if any, those drugs may have played.

A law enforcement official confirmed to the Associated Press that investigators were looking into whether Prince died from a drug overdose and whether a doctor was prescribing him drugs in the weeks before his death.

They are also looking at whether a doctor was on a plane that made an emergency landing in Illinois less than a week before the singer died. He was taken to a hospital in Illinois, but was treated and released a few hours later.

A vault containing unreleased Prince songs was found at his estate and will be drilled open by the company with temporary authority over his estate, according to ABC News.

He told US TV programme The View about his unreleased music in 2012.

"One day, someone will release them. I don't know that I'll get to release them," he said. "There's just so many."

Enough music was apparently left behind to release an album a year for the next century.

His former recording engineer, Susan Rodgers, said: "We could put out more work in a month than most people could do in a year or more."