A police lieutenant colonel suspected of involvement in the sex trafficking scandal in Mae Hong Son has been suspended from duty pending criminal and disciplinary investigations -- although he is still at large.

Deputy national police chief, Srivara Ransibrahmanakul, on Friday arrived in the northern province to follow up on the progress of a police investigation into the case which implicates state officials, police officers and a teacher.

According to media reports, four police officers who have been summoned to answer charges yesterday surrendered to investigators. Pol Gen Srivara led a team of investigators to search a house belonging to a police lieutenant colonel also summoned to report to investigators, only to find the house was empty with only a towel and roll-on deodorant left behind. The police officer's name was not disclosed.

It was found the police lieutenant colonel had signed out asking to leave on "official duties" on Thursday, Pol Gen Srivara said.

However, the police lieutenant colonel's commanding officer insisted he did not give his subordinate any assignments so this was deemed to be an unauthorised absence from duty, Pol Gen Srivara said.

Pol Gen Srivara said he had ordered the police lieutenant colonel to be suspended from duty along with a disciplinary probe into his absence from work, in addition to a criminal investigation relating to the sex-trafficking scandal.

Pol Gen Srivara said nine local police officers in Mae Hong Son faced charges in connection with the case.

Among the nine is Yutthachai Thongchart, a local police senior sergeant-major from Nam Phieng Din station, who was apprehended previously for involvement in the flesh trade.

Of the remaining eight officers, seven have now turned themselves in to investigators, except the police lieutenant colonel who has still failed to report.

Pol Gen Srivara said that if evidence links anyone to the sex trafficking trade, police will take legal action against them immediately.

For those who face summonses and fail to report, investigators will issue another summons, and if they fail to turn themselves in again, a warrant will be requested from the court for their arrest, Pol Gen Srivara said.

He said a Mae Hong Son teacher, who is another suspect in the sex trafficking scandal and has been summonsed, has moved to another province. Investigators will call the teacher in for questioning.

Investigators were gathering evidence as they were building a case against Mae Hong Son governor Suebsak Iamwicharn who is among the officials accused of involvement in the sex scandal.

He was transferred to an inactive post at the Office of the Interior Permanent Secretary, pending a probe.

The scandal broke after the mother of a 17-year-old girl -- one of the victims allegedly forced into the flesh trade in the province -- lodged a complaint with Provincial Police Region 5 in charge of the North, accusing several high-ranking state officials of being involved in the racket. However, the mother, 43, who was identified only as Nampetch, decided to go to the Anti-Trafficking in Persons Division after she said the probe had moved forward at a snail's pace.