HOUSTON -- A man was charged Friday, accused of intentionally administering fake flu shots to hundreds of ExxonMobil employees, KPRC Local 2 reported.

Iyad Abu El Hawa, 35, is accused of attempting to defraud Medicare by giving fake flu vaccines, according to U.S. Attorney Chuck Rosenberg. Officials said El Hawa substituted a purified form of water for the vaccine.

Investigators said the bogus flu shots were given at an ExxonMobil health fair on Oct. 19 and 20 at the Baytown refinery. About 1,100 people received them.

According to court papers, El Hawa admitted to giving the fake shots to the ExxonMobil employees and also to 14 senior citizens at a La Porte nursing home last Friday.

He also told federal agents he had done it other times, as well, officials said.

"This is a callous and disturbing crime. Mr. El Hawa purposely put at risk many, many people. He put at risk those who thought they were being inoculated against the flu, but in fact, were not. He also put at risk those who received a fake vaccine and those for whom that provide care," Rosenberg said.

El Hawa is the owner of Comfort & Care Home Health, 10101 Harwin, and operates two other facilities -- America Home Health and Universal Home Health Care Services.

He was arrested and placed in federal custody Thursday night. If convicted, El Hawa faces up to 10 years in prison and a $250,000 fine. More charges could be filed, prosecutors said.

Officials said the case came to light when a nurse called the FBI after El Hawa's employees were unable to supply a lot number for the vaccine.