A potentially toxic chemical that has run off former military bases and manufacturing sites to contaminate drinking water in parts of suburban Philadelphia and South Jersey has shown up in a Camden County borough’s water supply.

Bellmawr Borough ordered one of its two water treatment facilities shut down Thursday, three weeks after the New Jersey Department of Environmental Protection notified the borough of the contamination. It marked one of the first times New Jersey’s newly established drinking-water standard for a chemical known as PFNA set off alarm bells for a municipal water authority.

The testing measured PFNA at an average level higher than the state’s limit by about 6 parts per trillion, the borough said in a letter to residents. The borough has a population of about 11,500.

At that low level, the water was still safe to drink, the DEP told Bellmawr, the borough said in a statement. The contamination does not pose a health emergency for residents.

Local officials must bring the water system into compliance with the state standard within a year, but “in an absolute abundance of caution,” the borough decided to immediately shut down the contaminated water supply.

The chemical is a type of PFAS, a large family of substances that have been linked to cancer and other health problems and have been found in the drinking water of millions of Americans. It cannot be boiled out of water and requires costly treatment systems to remove.

Elsewhere in New Jersey, officials have pointed to former Solvay, DuPont, and 3M manufacturing sites as the culprits of PFAS contamination in areas including Gloucester, Passaic, Middlesex, and Salem Counties. In Pennsylvania, the chemicals poured off military bases in Bucks and Montgomery Counties.

This year, New Jersey became the first state in the country to set a drinking-water standard for one of the PFAS chemicals with its 13-part-per-trillion limit on PFNA. New Jersey plans to regulate two other types; Pennsylvania and a handful of other states are working on their own standards.

PFNA was used at a Solvay facility in West Deptford, Gloucester County — not far from Bellmawr — and has been found in high concentrations in nearby public water supplies, a 2015 New Jersey Drinking Water Quality Institute report documented.

“Large amounts of PFNA were discharged to air, soil, and surface water at facilities where it was used as a processing aid,” the report said.

In March, the DEP ordered Solvay and other companies to pay for cleaning up PFAS contamination in New Jersey; at the time, Solvay said it was in touch with DEP and implementing remediation. The state has already spent more than $3 million on the West Deptford site.

“The DEP needs to take immediate steps on mitigating this critical issue and hold polluters accountable,” New Jersey Sierra Club director Jeff Tittel said in a statement Thursday.

Officials in Bellmawr hope to determine the origin of the PFNA and bring the treatment facility back online quickly. In the meantime, they said, water service to residents will be uninterrupted.