McDonald's is investing $100 million to bring customers back to stores after an outbreak of E. coli food poisoning tied to onions on the fast-food giant's Quarter Pounder hamburgers.

The investments include $65 million that will go directly to the hardest-hit franchises, the company said.

The U.S. Centers for Disease Control and Prevention has said that slivered onions on the Quarter Pounders were the likely source of the E. coli. Taylor Farms in California recalled onions potentially linked to the outbreak.

The E. coli outbreak has sickened 104 people in 14 states, federal health officials said in an update on Wednesday.

At least 34 people have been hospitalized, and four developed hemolytic uremic syndrome (HUS), a serious condition that can cause kidney failure. An 88-year-old man who resided in Grand Junction, Colorado, died, as previously reported. The illnesses began at the end of September, and the most recent onset of illness occurred as of Oct. 21, according to the U.S. Food and Drug Administration.

The Food and Drug Administration has said that "there does not appear to be a continued food safety concern related to this outbreak at McDonald's restaurants."

However, the outbreak hurt the company's sales.

Quarter Pounders were removed from menus in several states in the early days of the outbreak.

In a statement Wednesday obtained by CBS News, McDonald's said it had found an "alternate supplier" for the approximately 900 restaurants that had temporarily stopped serving Quarter Pounders with slivered onions.

"Over the past week, these restaurants resumed the sale of Quarter Pounder burgers with slivered onions," McDonald's said.

CBS News reached out to McDonald's on Saturday for a statement regarding the reported investment.