A South Royalton restaurant voluntarily closed for several days recently and switched food vendors after being contacted by state officials who are investigating an E. coli “cluster” that has sickened at least five people.

Meanwhile, state officials have released few details about their investigation, including the potential source of the contamination or how widespread the risk may be.

Jason Merrill, executive chef at Worthy Burger, said the Vermont Department of Health approached the restaurant’s leadership team last week and asked them to consider changing some of their food vendors out of precaution.

“They haven’t told me which ones they wanted me to change, so I changed pretty much all of my vendors,” Merrill said, noting he uses six or seven area farms to supply ingredients for the menu at Worthy Burger, which specializes in locally sourced food.

At least five people have contracted E. coli in what state officials have referred to as a “cluster,” according to the Vermont Department of Health. The locations of the five laboratory-confirmed cases, as well as a sixth case listed as “probable,” haven’t been divulged by health officials nor is it clear how the six cases are connected.

The health department is working on identifying the source of the contamination, spokesman Ben Truman said on Thursday.