Jason Gerwig, a public information officer for the DuPage County Health Department, said his agency is looking at a Lombard restaurant as a possible source for the outbreak, and said the restaurant had been temporarily closed at 5 p.m. Friday as part of the investigation. He did not want to name the restaurant until he had received further confirmation that the four people with confirmed cases of E. coli had been there, he said, and would not be able to get that confirmation until Monday.