Officials are offering free preventive treatment to people possibly exposed to hepatitis A at a McDonald's restaurant near the Quad Cities.

Kevin Murphy operates the McDonald's restaurant in Milan. He says the restaurant learned from health officials on July 13 that one of his workers had been diagnosed with the virus.

That worker was diagnosed June 17. State health officials say they didn't know about the case until July 13, and authorities are trying to figure out why the case went unreported for so long.

Another infected Milan McDonald's employee came to work on seven days in July, possibly spreading the virus to patrons. It isn't clear when health officials or McDonald's learned about the second worker.

An estimated 10,000 people who ate at the restaurant are being urged to get preventive shots.

"Once we were notified of this matter by the Rock Island County Health Department on July 13, we took immediate corrective action to address their concerns," said Kevin Murphy, McDonald's franchisee. "No one ill knowingly worked in our restaurant once we were notified. The Rock Island County Health Department has repeatedly said that they have not confirmed the source of the outbreak. In fact, they believe, based on the number of confirmed cases, that it's most likely there are multiple sources."

The Associated Press contributed to this story.