Construction on Citadel's new headquarters in Brickell, Miami, has been ordered to stop following an equipment collapse at the site last week. At least four people sustained minor injuries and were transported to a hospital as a result of the accident. The halted project is a multi-billion-dollar tower planned for the area by Citadel, the hedge fund founded by billionaire Ken Griffin. The firm operates independently from its affiliated market maker, Citadel Securities.