The flood of heroin coming into and going out of New York City has surged to the highest levels in more than two decades, alarming law enforcement officials who say that bigger players are now entering the market to sell the drug here and to feed a growing appetite along the East Coast.

The amount of heroin seized in investigations involving the city’s special narcotics prosecutor has already surpassed last year’s totals, and is higher than any year going back to 1991.

The drug makes its way here in trucks rumbling north from Mexico; as they get closer to New York, they park at truck stops or warehouses to transfer loads of heroin to cars bound for mills in the Bronx or Upper Manhattan and, eventually, to users along the Eastern Seaboard at prices ranging from $6 to $10 per glassine envelope.

The rise in heroin use nationwide has been well documented, as the drug has created addicts and caused the deaths of well-known figures, like the actor Philip Seymour Hoffman, and young people in middle-class families from Staten Island to Vermont.