The commissioner said it's believed that samples pulled from wells in Upper Township last month were knowingly tampered with by someone who had access after they were taken from the wells.
The meeting was packed Monday night in Upper Township to hear the commissioner address the mercury levels as he appeared virtually at the meeting.
Residents also asked questions and raised concerns.
This all started when one resident reported high mercury levels in a private residential well. That triggered tests for other private wells in the area.
Those tests - conducted by a local company - came back showing dangerously high levels of mercury, according to officials.
The DEP got involved and did independent testing, which came back either non-detectable for mercury or well below the standard.
The DEP has not named the company that produced these high samples, saying they didn't want to impugn a person or company at this point in the investigation.
However, a township official confirmed the company was Cape Environmental Laboratory, which is a certified laboratory.
Action News spoke with the owner of the lab Monday afternoon, who says he is cooperating with the DEP, saying that he himself had been trying to figure out how results could be that high.
State officials called the offense a waste of government resources.
"Someone with access to the initial samples is believed to have knowingly tampered with those samples that resulted in high mercury readings," said NJ DEP Commissioner Shawn LaTourette.
"To be clear, the actions are shameful...it is downright inexcusable," said LaTourette.
The mayor of Upper Township Jay Newman said he was flabbergasted at this news from the DEP.
The investigation is ongoing. It's also being referred to the New Jersey Office of the Attorney General as a criminal matter.
Officials did not give many details on how they think this happened or why someone would do this.
The DEP said the state is working on retesting many of the wells in the area to ensure water is safe and will continue to pay for bottled water or in some cases relocation until that testing is complete.