The Cherry Hill Police Department is one of four added sites where people can drop off expired or unwanted prescription drugs to be destroyed under a state initiative intended to curb abuse of medications, Attorney General Jeffrey S. Chiesa said Thursday.

The state Department of Consumer Affairs had installed lockable metal boxes that resemble mailboxes at three other police departments in November, but residents turned in more pills than expected, making it expensive for the local agencies to destroy them.

Under the expansion of the "Project Medicine Drop" program, a Morristown company that converts waste to energy will cover the cost of destroying the drugs, easing the burden on local law enforcement agencies, Chiesa said.

Disposing of a ton of drugs costs $300 to $400, a spokesman for Covanta Energy said.

State officials hope to install at least one drop box in each of the state's 21 counties by the end of the year, Chiesa said.

"This box invites members of the public to come in and dispose of their excess household medications, no questions asked, in a way that's safe and secure," he told reporters at the Cherry Hill Municipal Building.

The program complements a one-day annual collection of prescription drugs - April 28 this year at various locations - held by the U.S. Drug Enforcement Administration.

Cherry Hill Police Chief Rick Del Campo said the department saw an advertisement in a police magazine and volunteered to be part of the expansion to give residents who may miss the DEA's program a chance to get rid of drugs at any time.

The drop box is in the lobby of City Hall in front of the Police Department. It is bolted to the ground and under video surveillance.

The other new locations are: the Somerset County Sheriff's Office and the Lower Township and Toms River Police Departments.

The three initial sites were the Little Falls, Seaside Heights, and Vineland Police Departments. Since drop boxes were installed in November, those locations have received about 400 pounds of pills, officials said.

Chiesa noted part of the impetus behind the program: Abuse of prescription drugs kills more people than heroin and cocaine combined.

"These drugs are incredibly addictive," he said. "Unless you're under the close supervision of a physician when you're taking these medications, you're really exposing yourself to long-term damage, which can lead to abuse of other medications."

In New Jersey, there were 7,200 admissions to state-licensed or certified substance-abuse programs for prescription-painkiller abuse in 2010 - an increase of about 225 percent from 2,210 in 2005, according to state officials.

Two in five teenagers mistakenly believe prescription drugs are "much safer" than illegal drugs, they said.

Linda Surks said her teenage son Jason, who died of a prescription-drug overdose in 2003, hadn't seen a danger in using the drugs.

"He had the misperception, as many people do, that because they're legal drugs, because they're FDA-approved, they're safer than other drugs," said Surks, a coordinator with the National Council on Alcoholism and Drug Dependence of Middlesex County who accompanied Chiesa.

Covanta has offered to destroy household prescription drugs collected by communities and police agencies nationwide free of charge since 2010.

The company will incinerate the drugs in its facilities in Newark, Rahway, and Oxford, which process municipal solid waste to create steam and electricity.

The process is approved by the Department of Environmental Protection, state officials said.

Company officials said destroying the drugs that way instead of flushing them down the toilet or disposing of them in landfills protects the water supply from potential contamination.