By Cara Lombardo and Miriam Gottfried

A group of buyout investors has made a takeover offer for railroad operator Kansas City Southern, which has a market value of more than $17 billion, according to people familiar with the matter.

Blackstone Group Inc. and Global Infrastructure Partners submitted the bid after a previous approach was rebuffed, the people said. It is unclear whether Kansas City Southern will be receptive this time and details of the offer couldn't be learned.

Kansas City Southern shares traded around $184.78 Wednesday afternoon, giving the Missouri-based company a market value of about $17.5 billion.

The Wall Street Journal reported in late July that the private-equity firms were contemplating a takeover bid for the railroad. Since then, Kansas City Southern's stock price has jumped on hopes of a deal.

Kansas City Southern is working with Morgan Stanley to consider the bid, some of the people said.

(More to come)

Write to Cara Lombardo at cara.lombardo@wsj.com and Miriam Gottfried at Miriam.Gottfried@wsj.com