BANGKOK (The Nation/Asia News Network) - A police major-general who used to head Bangkok's Metropolitan Police Division 5 as well as six other police officers are under probe for allegedly allowing Red Bull heir Vorayuth "Boss" Yoovidhya evade prosecution over a fatal hit-and-run accident, a source said.

The National Anti-Corruption Commission (NACC) is investigating Maj-Gen Krit Piakaew and the other officers, the source at NACC said on Wednesday (July 19).

Vorayuth, a 31-year-old grandson of Red Bull co-founder Chaleo Yoovidhya, is accused of running over and killing 47-year-old patrolman Police Senior Sergeant-Major Wichean Klinprasert on Bangkok's Sukhumvit Road five years ago.

The policeman's body was dragged about 200m along the road.

Vorayuth, who has repeatedly ignored previous summonses and has yet to be charged with a crime, was due to face his accusers in April but days before that encounter he left Thailand. He has reportedly been spotted in the United States.

An NACC sub-panel was established late last month to investigate Krit; his two former deputies Pol Colonel Sukhun Phrommayon and Pol Colonel Traimet U-thai; Thonglor Police Station superintendent Pol Colonel Chumpol Phumpoung; and three Thonglor investigators, Pol Colonel Samrit Ketyaem, Pol Lt-Colonel Wibul Thinwattanakul and Pol Lt-Colonel Wiradol Tabtimdee.

The officers are accused of allowing Vorayuth to avoid drunk driving, speeding and substance abuse charges as well as failing to timely issue an arrest warrant for Vorayuth to face an indictment decision earlier this year.

In the face of growing criticism over the perceived delay in Vorayuth's extradition, Metropolitan Police Chief Lt-General Sanit Mahathavorn on Tuesday said he would coordinate with a private company currently translating a 34-page document requesting the extradition of Vorayuth.

Once the document is translated, police will request the Foreign Affairs Ministry's help to proceed, he added.

The statute of limitation has expired for charges of speeding and reckless driving causing property damage, but Vorayuth remains accused of reckless driving resulting in death, which has a 15-year statute of limitation, and refusing to stop to assist a victim, for which the statute ends in September.

The first offence carries a maximum jail term of 10 years and the latter six months.