Underage decoys were able to purchase liquor at 58% of more than 900 retailers -- pharmacies, groceries and liquor stores -- they visited throughout the city between April and September, the New York City Department of Health and Mental Hygiene announced Sunday.

A dedicated unit of underage decoys was created by a grant from the Health Department to the New York State Liquor Authority. The 911 businesses visited by the decoys represent 10% of all NYC retailers with liquor licenses, according to the Health Department.

The department is sending letters to retailers today encouraging the businesses to check IDs and seek additional staff training to stop sales to minors, while asking for their help in reducing the negative effects of underage drinking. It is also ramping up business education efforts and partnering with the NYPD to enforce underage drinking laws, as costs associated with teen tippling exceed $1 billion per year in New York State, according to the Health Department.

People who start drinking early are not only more likely to develop an alcohol addiction, but are more likely to have unprotected sex, become involved in fights and cause and die in fatal car accidents. Alcohol related injuries (homicides, suicides and accidents) claim the lives of 5,000 people under the age of 21 each year in the U.S.

"Reducing access to alcohol will ... curtail underage drinking and reduce the nearly 7,000 alcohol-related emergency room visits among New Yorkers under age 21," said NYC Health Department Commissioner Mary T. Bassett in a statement.

Licensees charged with selling booze to minors can face up to $10,000 in fines per violation, with fines starting at $2,500, and suspension or revocation of a license if violations of the law persist.