BERLIN, Dec 22 (Reuters) - Tesla (TSLA.O) and relevant authorities have submitted all the documents necessary for the approval process for its planned factory near Berlin, the environment ministry of the German state of Brandenburg said on Wednesday. The approval process is still ongoing, the ministry said. Tesla could not be immediately reached for comment. Due to environmental resistance and red tape, it remained unclear when the first vehicles will roll off the production line at the site. Brandenburg premier Dietmar Woidke had recently suggested a decision might come in early 2022. Tesla has repeatedly had to push back the expected opening of the factory and Chief Executive Elon Musk has regularly travelled to Germany to check on the plant"s progress, criticising German bureaucracy for slowing down construction. Since Tesla expanded its original proposal to include a battery factory, the construction plans had to undergo a renewed process of public consultation which ended on Nov. 22. The response to all objections raised in that consultation is a prerequisite for a final building permit. Currently, Tesla is only working on the factory on the basis of preliminary building permits.