TRENTON — The state Department of Health is investigating  E. coli cases in at least four counties that may be connected to the same restaurant chain.

The cases were reported in Hunterdon, Middlesex, Somerset and Warren counties with the first being reported by a hospital on March 28, spokeswoman Donna Leusner told New Jersey 101.5.

The cases may be connected to different locations of a restaurant chain, Leusner told the Patch of Bridgewater. She would not name the chain until an investigation could make a stronger connection.

Leusner told the news site that the investigation involves tracking the source of the food product consumed, speaking with those infected and the employees of the restaurants potentially involved.

E. coli, or Escherichia coli, is a bacteria that normally lives harmlessly in the intestines of people and animals, according to the CDC. Some types are pathogenic and can cause illness through exposure to contaminated food or water or contact with animals or other people.

Symptoms include severe stomach cramps, diarrhea (often bloody), and vomiting.

Someone who is exposed may have symptoms within three or four days but there are cases where it starts within a day.

Some infections with recovery within five to seven days. Other cases can be severe and even life threatening.

The CDC recommends that you consult a doctor if you have diarrhea that lasts for more than three days or is accompanied by high fever, blood, or so much vomiting that you cannot keep liquids down and you pass very little urine.

E.mcoli is prevented by thorough hand washing after using the bathroom or changing a diaper before and after food preparation and contact with animals.