Berkshire Hathaway-owned BNSF Railway is working with Goldman Sachs to evaluate a takeover of a rival U.S. freight railroad, according to people familiar with the matter cited by Reuters and other industry reports. The sources said BNSF has not yet decided whether it will pursue CSX Corp. or Norfolk Southern Corp., the two major East-Coast carriers regularly named in recent consolidation speculation. Semafor first reported the discussions, which come as Union Pacific weighs its own bid for Norfolk Southern in a wave of dealmaking that could redraw the country’s rail map. No formal offer has been made and the companies involved declined to comment. A transaction would face close scrutiny from the U.S. Surface Transportation Board, whose approval is required for large rail mergers. Investors reacted quickly: CSX shares gained roughly 4% on the report, while Norfolk Southern climbed about 2.4% in after-hours trading.