A doctor who injected Michael Jackson with a painkiller shortly before his death was being sought by police on Friday afternoon.

They want to question the physician about the last hours of the 50-year-old star, who died of a suspected heart attack at his Los Angeles home.

A law enforcement source has revealed that the doctor cannot be located.

Jackson`s personal physician thought to be Dr Tohme Tohme was with him when he collapsed shortly after noon (8pm UK time). Paramedics arrived within four minutes of being called to find the doctor trying to revive the star, who had stopped breathing.

A spokesman for Los Angeles Police Department confirmed that officers were looking for a doctor who was at the star`s house at the time of his collapse.

He said: We are looking for him because that is a normal part of an investigation like this. We cannot confirm the name of the doctor.

The hunt was revealed by TMZ the website which broke news of his death.

The site said that the doctor`s BMW was seized from Jackson`s home. It has emerged that the star received an injection of the morphine-like synthetic drug Demerol a few hours before he suffered the heart attack.

Jackson`s family and friends believed his heart attack was caused by the pressure to perform at London`s O2 arena.

Family lawyer Brian Oxman blamed enablers for pushing Jackson too hard physically in preparation for the 50 comeback concerts in London that were due to start on 13 July.

Former Jackson 5 publicist Arthur Phoenix said he had warned the singer`s family that he was too frail to perform at the O2.

Jackson himself was left fuming after concert promoters booked 50 gigs.

He told fans on his website this month: I don`t know how I`m going to do 50 shows. I`m not a big eater I need to put some weight on.

I`m really angry with them booking me up to do 50 shows. I only wanted to do 10, and take the tour around the world to other cities, not 50 in one place. I went to bed knowing I sold 10 dates, and woke up to the news I was booked to do 50.

Speculation is now also turning to the fate of his three children Prince Michael, 12, Paris, 11, and seven-year-old Prince Michael II who were being looked after by Jackson`s mother, Katherine.

Lawyer Mr Oxman said of the death: This was something which I feared and something which I warned about. This is a case of abuse of medication, unless there is another cause that I don`t know about.

The people surrounding him have been enabling him. If you think the case of Anna Nicole Smith [the model who died from an overdose] was abuse then that is nothing in comparison to what we have been seeing in Michael Jackson`s life. Where there is smoke there is fire.

Mr Phoenix added: As a family friend, I let Joe (father) and Tito (brother) know my concerns. Michael put his heart and soul into these shows?... ?but his heart and his physical being just wouldn`t hold out.

Mr Phoenix claimed that family members shared his opinion but were too afraid to speak about their concerns.

He added: The family is in mourning right now. They are devastated and very hurt. The world of entertainment has suffered a great loss, the biggest since the death of Elvis Presley.

Paramedics spent 42 minutes treating Jackson at the house but he did not regain consciousness. He was declared dead at 2.26pm local time at the UCLA Medical Centre, about two miles from his home near Sunset Boulevard, after a further hour spent trying to save him.

Fans around the world were stunned by the news. Jackson`s 1982 album Thriller, which remains the biggest-selling album of all time, went immediately to No1 in the iTunes chart while Twitter, the online messaging service, was receiving 5,000 messages a minute.

Jermaine Jackson told reporters outside the hospital: This is hard. My brother, the legendary king of pop, passed away on Thursday, June 25 2009 at 2.26pm. It is believed he passed away of cardiac arrest.

Gossip websites were full of claims over the circumstances. One, quoting a hospital source, claimed Jackson had collapsed after an injection of the painkiller Demerol.

The source said: Shortly after taking the Demerol he started to experience slow, shallow breathing. His breathing gradually got slower and slower until it stopped.

Sources suggest Jackson had also been taking other prescription painkillers and anti-anxiety drugs Xanax and Zoloft in recent months.

Mr Oxman said the singer was taking the drugs to deal with past injuries, including a broken back, which were sabotaging his concert rehearsals: His use of medications had come in the way and injuries he had sustained performing had got in the way.

Another brother, Marlon, said the Jacksons were stunned . Janet Jackson flew to Los Angeles from a film shoot and their parents also arrived last night.

Jackson`s ex-wives Debbie Rowe and Lisa Marie Presley spoke of their shock. Ms Rowe, who gave birth to two of Jackson`s children Prince and Paris was inconsolable . Presley said she was heartbroken for his children: I am so very sad and confused.

thisislondon.co.uk