The number of infections caused by tainted milk from a Beaver County dairy continues to rise, as state officials undertake an investigation into the farm. Five people were sickened by the bad milk last week, and that number climbed to eight today. The Pennsylvania Departments of Health and Agriculture have teamed up to begin testing for bacteria at the Brunton Dairy in Aliquippa. Department of Health physician Andre Weltman said this kind of investigation is rare. It's also challenging and time-consuming. Weltman said scientists must sample everything in the milk production process, in an attempt to find where the 'yersinia' bacteria came from – but he said the source of the problem may never be discovered. Weltman said the bacteria, which causes a stomach sickness called 'yersiniosis,' shouldn't be taken lightly. "This bacteria can be serious, and like a lot of other infections of this type, it tends to go after the very young and the very old, and those are the most vulnerable populations," said Weltman. "So yes, 'yersinia' could kill someone, although fortunately we don't have any deaths, at least this far in this outbreak." Allison Longenberger of the Centers for Disease Control and Prevention said she expects the number of 'yersiniosis' infections to rise. She said it can take up to 14 days for symptoms like diarrhea and fever to appear. Weltman said Brunton Dairy is cooperating with the investigation, and has stopped milk production. He said nobody should drink milk from that dairy until further notice.