Clare Nuttall in Almaty -

Three months after the assets of Uzbekistan's largest foreign investor, Zeromax, were seized by the State Security Service, mystery still surrounds the motive behind the move.

Zeromax is widely understood to have links with Gulnara Karimova, President Islam Karimov's daughter and Uzbekistan's richest woman with an estimated fortune of $570m. One theory is that the asset grab was part of a power struggle between Karimova and Prime Minister Shavkat Mirziyaev, who has been the driving force for a series of attacks on successful local entrepreneurs this year. Karimova's earlier appointment as Uzbekistan's ambassador to Spain indicates she is most likely planning a future outside the country.

More prosaically, Zeromax had become increasingly loaded with an estimated $500m of debt as it was forced, like other successful Uzbek businesses, to act as a banker to failing state enterprises. Signs the company was struggling financially came earlier this year when plans to build a $150m stadium for its football club Bunyodkor were abandoned. Bunyodkor also let go Luiz Felipe Scolari, the former Chelsea manager it had hired at vast expense less than a year earlier. The government found that Zeromax wasn't paying a lot of taxes, speculates one local entrepreneur. "The background of the company was really strong, but the state decided to punish them in the struggle against all strong local businessmen."

Yet there is another explanation - that Tashkent moved against Zeromax under pressure from Russia. While relations have warmed between Russia and Uzbekistan recently, Russian oil majors are understood to have resented Zeromax's dominance within the Uzbek economy, where its tentacles stretch across sectors from oil and gas to agriculture to textiles. There are rumours that after the asset seizure, 51% of Zeromax's shares were transferred to Uzbekistan's state energy company Uzbekneftegaz - the remaining 49% to an unnamed Russian investor.