A police spokesman said no one had been arrested in connection with Charitar's murder and investigations were continuing.

A police source said the technician had been assigned to work in Revenue Tower in 2005. Charitar's body was found on top of an air- conditioning unit in the machine room of the Environmental Protection Department office on the 33rd floor of the building in October of that year.

'Shortly after the murder, he had been among a lot of people interviewed by police as part of investigations. But the man was not arrested at that time,' the source said.

Officers were looking into possible clues and it was too early to say whether the technician was involved in the murder, the source said.

Charitar's body was found in the supposedly secure machine room on October 24, 2005, 12 days after she disappeared during a visit to Hong Kong. She was last seen boarding a hotel shuttle bus in Yau Ma Tei.

The body, with one stab wound in the side, was dumped on top of an air-conditioning unit 3 metres off the ground. Her hands were tied behind her back with two pieces of black plastic strapping. Her handbag, passport, a few hundred Hong Kong dollars, two mobile phones, two Thai bank credit cards and a pair of sunglasses were missing.

There was no security camera record of Charitar or her killer or killers entering the building.

Charitar had been in Hong Kong with her filmmaker boyfriend, who was planning to make a movie about a spate of mystery killings in a big city. The movie has since been scrapped.

Police have offered a HK$700,000 reward for information leading to the capture of her killer or killers.