Norfolk stock traded as high as $288.11, but closed at $278, down 0.8%, while Union Pacific stock lost 4.5%, closing at $220.52. The S&P 500 added 0.1% and the Dow Jones Industrial Average lost 0.7%.

Union Pacific Corp. could reach an agreement to acquire Norfolk Southern Corp. and create a transcontinental rail behemoth as soon as early next week, people familiar with the matter said.The deal, which would be the largest deal ever in the rail industry,

Union Pacific's adjusted profit grew to $1.8 billion in the second quarter as merger rumors to swirl around the nation's largest railroad.