Union Pacific is in talks to merge with Norfolk Southern, according to The Wall Street Journal, in a deal that would shake up the railroad business in America.The Journal cited people familiar with the matter.

Union Pacific is working with Morgan Stanley investment bankers to provide guidance on the potential acquisition of another Class I railroad, the online publication Semafor reported on Wednesday, citing people familiar with the matter.

Union Pacific currently has a market value of about $140 billion, while Norfolk Southern is valued at around $60 billion. Following news of the negotiations, shares of Norfolk Southern rose by 4% in after-hours trading, while Union Pacific’s stock fell roughly 2% before reversing to a slight gain.