UOL Group, its subsidiary United Industrial Corp (UIC), and investment holding company Haw Par Corp asked for a trading halt at 7.33am on Wednesday, "pending an announcement".
All three companies come under the United Overseas business owned by the Wee family, led by patriarch Wee Cho Yaw.
UOL currently owns 43.4 per cent of UIC, which in turn owns almost four-fifths of Singapore Land.