Seven suspects, including three Thai-American men and three police, have already been arrested.

Mark Hutchenson, 46, was rescued by a police SWAT team on Thursday after being held captive since Saturday.

Sukhansa, his wife, said four or five men in police uniform and plainclothes - including a Thai-American half-blood, Nicolas Pruksukkan, who claimed to be an FBI agent - had searched their condominium and made off with US$400,000 (Bt14 million) in cash.

They took Hutchenson hostage and demanded $800,000 for his release. She then reported the abduction to police.

A squad of 30 Metropolitan Police including commandos stormed a town house in Lat Phrao district and found Hutchenson chained and handcuffed with his face covered by a woollen cap.

Police Senior Sergeant-Major Suchart Muengkhunlong and Nicolas were arrested at the site. Suchart denied involvement in the extortion attempt, claiming that he was hired for Bt20,000 to guard the town house.

Yesterday more five suspects including two police were arrested. They were Metropolitan Police Sergeant Sathit Prasanphangsri and Crime Suppression Police Sergeant Prasertpan Punarittidej. The three civilians were Thai-American men - John and James McCleary, and Mongkol Sukkasem. Police also seized some Bt700,000 from the suspects.

All were charged with armed extortion, illegal detention, demanding ransom and malfeasance.

Metropolitan Police chief Lt-General Adisorn Nonsi said that according to information from the US Embassy, the McClearys are members of a ransom ring that fled arrest in the US and joined the gang of Lt-Colonel Thanapol Boonnak, an Immigration Police inspector temporarily assigned to the Internal Security Operations Command.

Police hold arrest warrants for the three suspects at large - Thanapol, Sergeant Adul Kamorn of Chokchai police station and a Thai-Dutch civilian, Samual, or Sam, Pasomthong.

Police believe Thanapol is the head of the kidnapping team and has run away with the rest of the money from Hutchenson's condo.

Adisorn said he had dismissed the three arrested officers, as they were under his bureau. They were denied bail as they had allegedly committed capital crimes. Their supervisors will be also investigated for negligence, he said.