Legal sources in Dubai have confirmed that among those in jail or in effect under house arrest over property-related bribery allegations are:

■ David Brown, architect and the middle eastern head of the Sunland Group, a Queensland development company which is part-owned by Mr Packer. Mr Brown has been interrogated at least eight times and has had his passport confiscated in relation to a bribery investigation.

■ Marcus Lee, until recently a senior executive with the Dubai Government-controlled Nakheel development company. He is a former executive with the local property companies Jones Lang LaSalle and Investa. Mr Lee is in jail, without charge, and is facing investigation over alleged bribery.

■ Mr Lee's Nakheel colleague Matthew Joyce, former managing director of the Dubai Waterfront project, is also in jail without charge over alleged bribery.

Until now, only the arrests of Mr Joyce and an unnamed colleague had been made public.

The three executives are of particular concern to lawyers and the Australian embassy because of the seriousness of the allegations and the uncertainty of their future. United Arab Emirates law allows suspects to be held indefinitely without charge.

It is understood the bribery allegations involve millions of dollars in consultancy payments by Sunland to Nakheel and a third party over a waterfront property purchase. Nakheel is one of four development companies linked to the Dubai Government and its ruler, Sheik Mohammed bin Rashid al-Maktoum.

Mr Lee and Mr Joyce have been held in solitary confinement since January 25. They have been allowed only limited access to lawyers and family.

Mr Joyce's and Mr Lee's Melbourne lawyer, Martin Amad, refused to identify Mr Lee by name or discuss details of the cases. But he said he was anxious for both men as they enter their second month in custody without charge.

"We're concerned for the welfare of the accused in custody where they've been kept in solitary confinement," he said. "Their physical and mental health has deteriorated. We are becoming increasingly frustrated at the time it seems to be taking for the prosecution authorities to investigate the matter."

Commenting on the 13 Australians under arrest in Dubai, a Department of Foreign Affairs and Trade spokesman said: "The United Arab Emirates legal system is different to the Australian legal system. People who are under investigation can be held in detention for long periods of time without bail."

Some fear people are being made scapegoats. "There is a lot of face-saving to be done," said one Melbourne property player well versed in business in Dubai. "The sheik can never be responsible, so somebody else has to be."

Sunland's managing director in Australia, Sahba Abedian, confirmed Mr Brown had been interviewed by police but insisted his company was not "implicated in the investigation".