WASHINGTON — The U.S. Supreme Court on Tuesday refused to block fines against a foreign-owned company that refuses to comply with a subpoena, apparently from special counsel Robert Mueller's prosecutors, to testify before a federal grand jury.

The identity of the company and the name of the country where it's based are unknown, because virtually all the legal documents are under seal.

The courthouse mystery began to unfold last summer when the company — identified only as a corporation owned by country A — resisted a grand jury subpoena, arguing that it's beyond the reach of U.S. law. But the company was found in contempt of court for refusing to comply and was ordered to pay a fine for every day it resisted.

The company appealed to the Supreme Court, and Chief Justice John Roberts put everything on hold in late December, including the fine of $50,000 a day. But Tuesday, in a brief unsigned order, the court lifted that stay, denying the company's request to block the fine.

It's impossible to tell, from the few public documents, who issued the subpoena. But it presumably involves Mueller's investigation, based on observing the lawyers, including some from his team.

The federal courthouse in Washington where the fight began went to unusual lengths to keep it secret, ordering reporters off an entire floor on a day when lawyers for both sides appeared in court.