Burma’s military authorities have confiscated six cars owned by detained ethnic Shan leader Hkun Htun Oo, his colleagues in Rangoon reported Friday.

The cars were confiscated earlier this week, Amyotheryei Win Naing said in a phone interview from the Burmese capital.

Hkun Htun Oo, chairman of the Shan Nationalities League for Democracy, or SNLD, was arrested along with eight other Shan leaders in early February and all are currently being held in Insein Prison, Rangoon.

The office of Hkun Htun Oo’s Overseas Courier Service company was shut down on February 14. The company distributed foreign newspapers and journals inside Burma. Most of the confiscated cars were used for company business.

It’s not yet clear on what charges the Shan leaders are being held. Some opposition leaders assume, however, that one motive for Hkun Htun Oo’s arrest is to weaken the ethnic umbrella organization, United Nationalities Alliance, or UNA. The UNA is a leading coalition of pro-democracy ethnic political parties, although it isn’t registered.

Win Naing said that Hkun Htun Oo was a key player within the UNA, and supported the organization financially. “Without him, the UNA can’t be active at all,” Win Naing added.  

Most activities of the UNA are prohibited. Last month, US State Department Spokesman Richard Boucher said Washington was “concerned that authorities have prohibited the United Nationalities Alliance (UNA), Burma’s leading coalition of pro-democracy ethnic political parties, from commemorating Union Day on February 12.”