PROVIDENCE, R.I. — Ten people in Rhode Island have died since March after apparently using a new synthetic opiate, health officials said Friday.

The state’s Department of Health has begun an investigation into the deaths. The federal Centers for Disease Control and Prevention is assisting in the work.

All those who died are believed to have been intravenous drug users, according to state health director Michael Fine. Most were residents of northern Rhode Island. Some died in hospitals and others were found dead in their homes, Fine told The Associated Press.

The drug’s chemical makeup has not yet been determined, Fine said.

“It appears to be a synthetic opioid that’s not heroin,” Fine said. “We will study the individuals who died and try to look for commonalities.”

State law carefully restricts the use of opiates and considers them a controlled substance that can only be used under a doctor’s care.

Fine said about 150 people die each year in Rhode Island after overdosing on prescription opiates. Another 100-150 people die each year after overdosing on illicit, non-prescription opiates.

Fine said the last death attributed to the drug occurred in mid-April. But he said he’s concerned that whoever manufactured the substance could make more.

Fine stressed that anyone addicted to opiates should seek help, and noted that a treatment option is now available without a prescription. Four Walgreens Pharmacies in Warwick are approved to dispense a drug known as Narcan used to treat opiate addiction. The drug is being made available as part of a pilot program with Miriam Hospital.

“A drug overdose is often a life-or-death situation and Narcan is a valuable resource that can help save lives,” he said.