UPDATE: New Jersey health officials have identified six additional patients who became infected after receiving injections to treat knee pain at a clinic in Wall Township, Monmouth County, bringing the total to 37.

Osteo Relief Institute Jersey Shore reopened on Tuesday with state and local inspectors on hand to ensure proper infection-control practices were followed, said Donna Leusner, a spokeswoman for the state Department of Health.

State and local investigators identified "infection control issues" during an inspection of the clinic on March 13, Leusner said.

At least 20 of the patients at Osteo Relief have needed surgery to treat their infections, said David A. Henry, health officer for the Monmouth County Regional Health Commission. The investigation is ongoing, he said.

The treatments offered at the clinic include injections with a substance containing hyaluronic acid. Some studies have suggested it can help patients, but in 2013, the American Academy of Orthopaedic Surgeons found there was not enough evidence to support its use.

In 2014, the most recent year for which public records are available, Medicare reimbursed the clinic more than $514,000 for such injections.

Osteo Relief voluntarily stopped administering injections on March 8 and has sent notification letters to patients who were treated this month, the Health Department said.

Most of the patients are from Ocean and Monmouth Counties, the department said.

The investigation involves the Health Department, the state Division of Consumer Affairs, and the Monmouth County Regional Health Commission.

The clinic's closure was first reported by News 12 New Jersey.