Dutch police are fighting a flood of cocaine that Colombian drug cartels are channeling through the Netherlands as their main gateway to Europe.

A bumper South American coca leaf harvest and a saturated U.S. market have combined to prompt the traffickers to send record amounts of the narcotic to Europe, police say.It's even more worrying, they say, that the size of each shipment is increasing, reflecting a more professional approach as the Colombian cartels wrest direct control of the trade in Europe.

Dutch police seized 4.3 tons of cocaine last year. That compared with 1.4 tons in 1989 and represents a 15-fold increase in just four years.

"Interpol have yet to produce official statistics, but our contacts with other police forces lead us to believe that more cocaine was seized here than anywhere else in Europe," Ernst Moeksis, spokesman for the national Police Research Bureau.

There is no sign, however, that these seizures have tightened supplies. Prices have held steady even after the biggest hauls.

Eddy Engelsman, head of the government's steering group on alcohol and drugs policy, believes only a tiny fraction of the cocaine - "certainly no higher than five to 10 percent" - is being found.

U.S. narcotics officials said in November that European imports in 1990 might be double the estimated 90 tons in 1989 as traffickers sought new outlets for surplus production.

The Police Research Bureau believes the Cali cartel, based in the southwest Colombian city of the same name, is spearheading the drive into Europe.

The cartel's sophisticated approach, including the use of marketing consultants and legal advisers, is giving it the edge over its better-known rival cartel from Medellin.

The Police Research Bureau fears Colombian interests will increasingly buy up legitimate Dutch companies as fronts for smuggling, concealing drugs in shipments of commodities such as coffee and fruit.

This was the technique used by a gang caught in the Netherlands last year with 2.6 tons of cocaine - a record for Europe - hidden in drums of frozen fruit juice.

While the Netherlands has gained a reputation as a Mecca for drug users since it decriminalized drug-taking, Engelsman does not think the influx of cocaine is to meet domestic demand.

"Holland is a transit country," he said. A survey on drug-taking in Amsterdam last month showed cocaine use had actually declined slightly since 1987, he said.

In addition, there is very little evidence of crack, the highly addictive cocaine derivative widely abused in the United States, being used in the Netherlands.