BANGKOK -- Thailand's prime minister responded Wednesday to growing public furor by ordering a probe into the dropping of criminal charges against a Thai heir to the Red Bull energy drink fortune accused of killing a policeman in a hit-and-run accident eight years ago.

The case involving Vorayuth Yoovidhya, whose family owns about half of the Red Bull empire, has highlighted longstanding allegations that the rich and powerful in Thailand enjoy impunity from the law. Forbes magazine's list of the richest families in Thailand places the Yoovidhya family second, with an estimated wealth of $20.2 billion.

Vorayuth, better known by the nickname 鈥淏oss,鈥� was wanted in connection with the Sept. 3, 2012, accident that occurred when his Ferrari struck and killed motorcycle policeman Sgt. Maj. Wichean Klunprasert.

The decision by the attorney general's office to not prosecute was made last month and announced last Friday at a police news conference.

Prime Minister Prayuth Chan-ocha's office announced Wednesday that he has ordered an investigation because the uproar over the case affected the credibility of the judicial system and its personnel and agencies. Prayuth said it was necessary to 鈥渟tart the fact-finding process to see what really happened and where the flaws lie, and fix them.鈥�

鈥淭here must be justice in Thai society applied equally without class discrimination,鈥� he said.

A 10-member investigating committee is to include government and parliamentary specialists on law, along with law deans at Bangkok's three top universities.

The investigation ordered by Prayuth is one of several sparked by the dropping of a charge against Vorayuth of causing death by reckless driving. The charge would not have expired until 15 years after the date of the crash.

It was the only remaining charge after ones of speeding, negligence causing property damage and failure to stop one's vehicle to assist a victim expired under a statute of limitations.

Both houses of Parliament announced hearings on the decision to drop charges, as did the police department and the attorney general's office. Representatives of the police and the attorney general's office presented themselves Wednesday before the House committee in charge of legal, judicial and human rights affairs.

After the 2012 accident, Vorayuth's lawyers managed to repeatedly put off any court appearances until April 2017, when a warrant was finally issued for his arrest a few days after he had left the country. His Thai passports were later revoked.

Vorayuth in exile enjoyed a jet-set lifestyle, flying in private Red Bull jets to attend Formula One races, going snowboarding in Japan and cruising in Venice, among other activities. An Associated Press investigation revealing his globe-trotting activities created outrage in Thailand.

At Friday's news conference, police spokesman Col. Krissana Pattanacharoen declared that the dropping of charges was done according to standard procedure and did not involve favouritism or double standards. He did not say exactly what motivated the action.

However, a document from the attorney general's office leaked to Thai media on Sunday cited two witnesses saying they had seen Vorayuth's Ferrari travelling safely within the 80 kilometres (50 miles) per hour speed limit, and that the motorcycle patrolman had recklessly cut in front of him. It also cited expert witnesses as determining that Vorayuth's car had been under the speed limit, even though police forensic experts had earlier determined that it had been moving as fast as 177 kph (110 mph).

Even some members of the Yoovidhya family expressed dismay Wednesday with the direction of Vorayuth's case. In an open letter, eight relatives said they had to 鈥渁pologize for the news of our family member that has caused anger, hatred, and dissatisfaction that is increasingly voiced in society.鈥�

鈥淲e have never given our opinion publicly out of respect to Vorayuth's (immediate) family and had hoped that Vorayuth would respond in a manner that is acceptable to society,鈥� said the letter, which was reported by most major Thai media. They said the recent negative news had made their situation unbearable, leading them to issue the letter.

They confirmed their respect for the judicial system, which 鈥渟hould provide justice to all without discrimination,鈥� and called on Vorayuth to prove himself to the family and society by following the proper path.

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Associated Press video journalist Tassanee Vejpongsa contributed to this report.