Stable prices for heroin and a likely increase in the drug's purity could lead to an increase in the number of overdose deaths, the U.N. drug agency warned.

The United Nations Office on Drugs and Crime (search) has alerted health officials globally about the risk, which comes after a survey indicated that opium production in Afghanistan (search) increased by 64 percent during 2004 as compared to the previous year.

Such increases in the past have lead to a surge in the number of deaths related to the drug, the agency said in a statement issued late Thursday.

"We know the worldwide supply will exceed demand for illicit heroin in 2005, and that an abundant supply of heroin is likely to result in rising levels of purity and substantial increases in the number of drug-related deaths," agency director Antonio Maria Costa (search) said in the statement.

"This is already happening in northern Russia (search)," he said.

Past experience show that Western Europe and neighboring regions are especially at risk, the agency said.

The agency's statistics show that the level of purity of the drug sold on the street depends on how much opium is produced. When opium production is high — as it was this year — a purer form of the drug can be expected to hit the streets.

More than 10,000 drug users die each year from overdoses involving heroin produced in Afghanistan. About 100,000 deaths per year are considered linked to abuse of the Afghan-cultivated drug, the Vienna-based agency said.