Two Pakistani military officers are under arrest in connection with two separate seizures of heroin totaling more than 800 pounds, according to officials who have been tracking the cases for signs of the government's willingness to crack down on high-level drug traffickers.

The size of the seizures, which would have a street value in the United States and Western Europe of about $50 million, has focused attention on the extent of drugtrafficking here and its impact on sensitive areas of this society.

Western experts estimate that 52 percent of the 6.5 tons of heroin flowing into the United States each year comes from Afghanistan, Pakistan and Iran -- an area now known as the Golden Crescent -- with most of that being shipped through Pakistan. For Europe, the figure is 85 percent.

Public attention recently has centered on the sudden upsurge in Pakistan's own opium production after several years of decline under government pressure. Pakistani officials admitted that production this year is likely to be between 100 and 160 metric tons, compared to 40 tons last year.

The two seizures are the largest ever made by the Pakistani narcotics control board. But in contrast with most drug hauls here, they have received almost no publicity.

Only one article, two brief paragraphs in an Urdu newspaper, has referred to the man arrested in the first case as an Army officer. Other short articles have called him a "member of a law-enforcing agency" or simply a government official.

Similarly, little publicity accompanied the arrest July 24 of an Air Force lieutenant after narcotics agents found 440 pounds of heroin in his car. Some newspapers reportedly did identify his military connection.

The delicate handling of the two huge heroin cases illustrates how powerful segments of society, such as the military, can affect treatment of a major case. Pakistan has just emerged from almost a decade under martial law and anything involving the military remains a very sensitive issue.

Western experts who closely monitor the narcotics trade in the region generally credit the government with making an effort to hold down cultivation of the opium poppy, despite this year's increase. But there is also a growing concern about heroin originating in Afghanistan.

Western experts say Pakistani authorities are aware of a number of trafficking kingpins -- men who make millions of dollars organizing drug-shipping rings -- but that few arrests are made. Pakistani authorities usually reply that their laws make available evidence insufficient.

Even when there are convictions, jail terms are usually brief.

"We can get a guy convicted for three years, a brief enough sentence in itself, and within two months he gets himself transferred to a comfortable room in the prison hospital, and four months later, he's out on the golf course. A man with money can buy himself out," said one expert.

"It has become like south Florida or Mexico," said another. "There are people making 3,000 rupees a month about $180 driving fancy cars and living in big expensive houses." Prime Minister Mohammed Khan Junejo in recent interviews and in statements during his recent visit to Washington pledged new tough antitrafficking laws. Western experts here are hopeful these will include new laws of evidence allowing use of wiretaps and video surveillance as well as tougher mandatory sentences.

"Most senior officials on the federal level are very strong on getting the job done. Where you run into problems is at the provincial level, where political interests and drug enforcement interests run into each other," said an observer.

In the first of the service cases, Maj. Said Shah Zahooruddin was turned over to military authorities shortly after his arrest on June 18, according to officials familiar with the case. Military spokesmen in Karachi said they were not aware of him.

In Islamabad, however, narcotics control board chairman Tilshad Najmuddin said that "as a serving military officer," Zahooruddin would be tried by a military tribunal. "I think it will take place very soon. It may have started already," Najmuddin said.

The major's wife has filed a petition seeking to have the case transferred to a civilian court.

According to officials, Zahooruddin was arrested while driving from the North-West Frontier Province to Karachi after narcotics control officials were tipped about a large drug shipment. A man driving the car and a woman also were taken into custody.

Zahooruddin was on assignment as a training officer for the national guard in the North-West Frontier Province, source for much of the opium grown in Pakistan or transported from Afghanistan. The opium often is refined in laboratories before shipment to Karachi or other departure points. Officials say much of the narcotics is being smuggled into India for transhipment, complicating the enforcement problem.

The major reportedly was previously assigned to the airport security command, which has a significant role in antinarcotics efforts.

In the second case, Air Force Lt. Khairur Rehman, 31, who is based in Peshawar, was arrested when agents apparently acting on a tip stopped his car as it approached Karachi and found the 440 pounds of heroin, according to officials familiar with the case.

Like Zahooruddin, Rehman has been turned over to military authorities and is expected to face court-martial after narcotics authorities complete their investigation.

The cases offer examples of problems faced by Pakistani and international narcotics officials as they try to stem the flow of heroin to the West.

"The opium is grown or processed in the North-West Frontier in movable laboratories and comes to Karachi by road," said one expert. "There is huge road traffic and the Pakistani authorities simply aren't equipped to stop it all. When they do get information, they will stop one," he said.

"There is an area called Sohrab Goth outside Karachi that is . . . a 'no-go' area for police," said one official. "It is absolutely full of heroin. It comes down in 200-kilo loads and is split up. Traffickers will send their men over for five or ten kilo buys," the official said. One kilo equals 2.2 pounds.

In a recent case, a Nigerian businessman was arrested at the Karachi airport after customs officers found more than 50 pounds of heroin hidden in a television set, according to Karachi customs collector Maqsood Butt. He said the businessman had purchased the heroin from two Afghans and that the transaction was typical of a new "African connection."

Officials say drugs are leaving South Asia for points in Africa and then making their way to Western Europe and the United States.