Subway co-founder Fred DeLuca, who at age 17 opened a submarine sandwich shop that he helped parlay into the world’s largest fast-food chain, died on Monday at age 67.

Subway confirmed his death on its website and said he had been scaling back his day-to-day role in operations.

“In 2013 while doing what he loved best, traveling around to visit with franchisees, DeLuca fell ill and was ultimately diagnosed with leukemia. Since that time he had been receiving treatments and still overseeing the brand as CEO,” the website statement said, adding that his sister, Suzanne Greco, was named as president.

The privately held company, based in Milford, Connecticut, did not immediately comment Tuesday if a successor had been named as chief executive.

DeLuca and family friend Peter Buck opened their first store in Bridgeport, Connecticut, under the name “Pete’s Super Submarines,” with the priciest sub selling for 69 cents. The name was changed to “Subway” in 1968, and the pair decided to franchise, or let others open Subway stores in exchange for fees. It currently has 27,000 U.S. locations.

In recent years, DeLuca helped lead the chain’s efforts to serve healthier meals that are lower in sodium. Since 2008, the company has reduced sodium in their sandwiches by nearly 30 percent on average, according to the Center for Science in the Public Interest.

Subway was the first fast-food chain to meet the American Heart Association’s Heart-Check Meal Certification Program nutritional criteria. The chain was also a long-time supporter of AHA healthy living initiatives, such as Jump Rope For Heart, Hoops For Heart and Heart Walks.

In total, the company has been a supporter of the AHA for more than 15 years, totaling more than $17 million.

DeLuca is survived by his wife, son and sister, according to Subway.