Usher performs next to the casket during memorial services for pop star Michael Jackson in Los Angeles July 7, 2009. REUTERS/Mario Anzuoni

Burial plans for Michael Jackson were a mystery Wednesday as attention returned to doctors who may have prescribed powerful drugs for the entertainer.

Sales of Jackson's albums soared for a second week, with his solo albums jumping another 90 percent to 800,000 copies in the United States, Nielsen SoundScan said.

A day after Jackson's casket was taken to a Los Angeles arena for a star-studded public memorial for the Thriller singer, the whereabouts of his body were unknown and there was no information about where or when he might be buried.

The Jackson family spokesman did not return calls for comment.

The Los Angeles coroner's office has released a death certificate that listed the cause of Jackson's June 25 cardiac arrest as deferred.

Media reports said the coroner's office was conducting neuropathology tests on part of Jackson's brain, which could be behind the delay in the family's burial plans.

Police and coroner's officials already have removed bags of drugs and medical evidence from Jackson's rented mansion and the results of toxicology tests are expected in about four weeks.

DERMATOLOGIST SAYS HE'S NOT TARGET

One of Jackson's doctors, Beverly Hills dermatologist Arnold Klein, Wednesday denied he was a target of the police investigation and said he had never prescribed Jackson dangerous drugs.

I was not one of the doctors who participated in giving him overdoses of drugs or too much of anything, Klein told ABC's Good Morning America in an interview.

In fact, I was the one who limited everything, who stopped everything ... I always was concerned about him. No matter what he wanted, someone would give it to him.

Klein also denied media reports from last week that he was the sperm donor of Jackson's two children with his ex-wife Debbie Rowe. To the best of my knowledge, I am not the father of these children, he said.

Jackson's music continued to enjoy the commercial success that eluded the King of Pop in recent years.

The singer's Number Ones compilation was the top-selling album in the United States on both the Billboard and SoundScan charts released Wednesday, with his 1982 album Thriller taking second place.

Jackson's public memorial Tuesday -- broadcast live on television around the world and streamed on the Internet -- was deemed the top funeral in global print and electronic media of the past 12 years.

The Global Language Monitor, which tracks media coverage through an algorithm, said Jackson had garnered 18 percent more stories than the death of Pope John Paul II in 2005.

It also won more attention that the deaths of former U.S. president Ronald Reagan in 2004, and Mother Teresa and Princess Diana in 1997, reflecting the explosion of news and comment on the Internet.