Eighteen Brazilians were left blind after surgeons apparently used unsterilized instruments during a cataract treatment campaign in an industrial suburb of Sao Paulo, officials said Thursday.

Sao Bernardo do Campo's city hall said 27 people were operated on Jan. 30 as part of the campaign, and 22 of them came down with an eye infection called endophthalmitis. It said 18 of them were left blind.

"Everything was fine when I left the hospital on the Saturday I was operated on. All was fine on Sunday. I could see perfectly well," Expedito Batista told the Globo TV network. "But when I woke up on Monday, it was all dark. I couldn't see a thing."

The city government said in an emailed statement that an investigation concluded that contamination took place during surgery "because of flaws in the disinfection and sterilization of the surgical instruments used."

Jose Luis de Macedo, the lawyer for the ophthalmology institute contracted to perform the surgeries, told reporters he could not comment because he has not read the report of the investigation by Sao Bernardo's Health Department.