By Mike Stone and Greg Roumeliotis

Jan 29 (Reuters) - Marquette Transportation Company LLC, a U.S. towboat operator, is exploring a sale that could value it at more than $1 billion and has attracted the interest of Dell Inc Chief Executive Officer Michael Dell, according to people familiar with the matter.

Marquette's owners, that include its founders and buyout firm KRG Capital Partners LLC, are working with investment bank Harris Williams & Co on an auction for the company that is already underway, the people said this week.

Private equity firms and family offices are vying for Marquette, including MSD Capital LP, the private investment firm of Michael Dell and his family, the people added.

Marquette has annual earnings before interest, tax, depreciation and amortization of close to $150 million, the people said.

The sources asked not to be identified because the sale process is confidential. Marquette, KRG, Harris Williams and MSD representatives did not immediately respond to requests for comment.

Paducah, Kentucky-based Marquette provides towboat services in the Mississippi River and other major waterways in the United States. It operates more than 120 boats and 850 barges, serving agricultural and energy companies.

The company was created in its current form in 2007 with the merger of three family-owned businesses and backing from KRG.

(Reporting by Mike Stone and Greg Roumeliotis in New York; editing by Andrew Hay)