UPDATE: On Friday, health officials in Warren County said the Phillipsburg-based Panera Bread is part of a "regional investigation" into the E. coli outbreak, which may involve other chain restaurants.

New Jersey health officials have confirmed two more E. coli cases in the state amid a cluster of cases spanning four counties and possibly linked to a restaurant chain.

The Warren County Health Department on Thursday confirmed that it -- along with the state -- was investigating certain Panera Bread restaurants at the potential source of exposure.

"The Department is investigating a possible association with a chain restaurant, but the association may be broader than a single chain restaurant," the state health department's statement said.

At least eight E. coli cases have been reported so far in Hunterdon, Middlesex, Somerset and Warren counties, the New Jersey Department of Health said in a statement on Friday.

The state Health Department said that all eight of the E. coli patients had been hospitalized but that five of the eight have been discharged.

In a statement Friday afternoon, the state noted that there may be other sources of the illnesses and that it is "still awaiting lab tests to determine if these cases are linked at all."

"It can be very difficult to determine where someone got sick ... They could have eaten at several restaurants, at home or eaten food purchased at a supermarket," the statement said.

Sarah Perramant, public health epidemiologist in Warren County, told NJ Advance Media on Thursday that health officials were looking into a Panera Bread in Phillipsburg one of the possible sources of E. coli exposure.

However, she noted that the matter remains under investigation.

Panera's corporate office, located in Sunset Hills, Missouri, did not return a request for comment on Friday.

There has only been a single E. coli case in Warren County so far, and some of the cases in the other counties were reported as far back as the third week of March, according to Perramant.

She stressed that people should not be overly concerned, saying that illness from E. coli is typically not that severe.

Most strains of E. coli are not harmful. However, the bacteria can still cause some awful symptoms, including diarrhea, abdominal pain, fever and vomiting.

The state Department of Health reiterated on Friday that it plans to conduct many interviews with those who have gotten sick to gather food history data.

Once the source of the E. coli is pinned down, it will be tested in a lab. The state will then send its findings to the Centers for Disease Control and Prevention for confirmation, officials have said.

Nick Falsone for LehighValleyLive.com contributed to this report.

Spencer Kent may be reached at skent@njadvancemedia.com. Follow him on Twitter @SpencerMKent. Find the Find NJ.com on Facebook.

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