WASHINGTON — The U.S. Army has investigated 56 soldiers in Afghanistan on suspicion of using or distributing heroin, morphine or other opiates during 2010 and 2011, newly obtained data shows. Eight soldiers died of drug overdoses during that time.

While the cases represent just a slice of possible drug use by U.S. troops in Afghanistan, they provide a somber snapshot of the illicit trade in the war zone: young Afghans peddling heroin, soldiers dying after mixing cocktails of opiates, troops stealing from medical bags, Afghan soldiers and police dealing drugs to their U.S. comrades.

In a country awash with poppy fields that provide up to 90 percent of the world’s opium, the U.S. military struggles to keep an eye on its far-flung troops and monitor for substance abuse.

U.S. Army officials said that while the presence of such readily available opium, the raw ingredient for heroin, is a concern, opiate abuse has not been a pervasive problem for troops in Afghanistan.

“We have seen sporadic cases of it, but we do not see it as a widespread problem, and we have the means to check,” said Col. Tom Collins, an Army spokesman.

The data represents only the criminal investigations done by Army Criminal Investigation Command involving soldiers in Afghanistan during those two years. The cases, therefore, are just a piece of the broader drug use statistics released by the Army this year reporting nearly 70,000 drug offenses by roughly 36,000 soldiers between 2006-2011. The number of offenses increased from about 9,400 in 2010 to about 11,200 in 2011.

The overdose totals for the two years, however, are double the number that the Defense Department has reported as drug-related deaths in Afghanistan for the past decade. Defense officials suggested that additional deaths may have been categorized as “other” or were still under investigation when the statistics were submitted.

The data was requested by conservative watchdog group Judicial Watch and obtained by the Associated Press. The Navy, Air Force and Marine Corps have not yet responded to the request for similar information. The Army reports blacked out the names of the soldiers who were under investigation as well any resolution of their cases or punishments they may have received.

Tom Fitton, president of Judicial Watch, said the numbers signal the need for the military leadership to be more vigilant about watching and warning troops in Afghanistan about drug abuse. He said the worry is that “the danger, including the danger of dying, hasn’t been fully acknowledged by the military and it needs to be.”

Army officials said they do random drug testing through the service and the goal is that every soldier is tested at least once a year. Top Army leaders have said they have not met that goal, but have been working steadily to substantially increase the number of those tested each year.

The officials also said the Army’s Criminal Investigative Division has quarterly drug statistics that show that drug use by troops in Afghanistan is not greater than that of troops in installations back in the United States and there is less of a variance in drugs used by troops in Afghanistan.

According to Army data, an average of 1.38 million urine samples have been tested annually over the past five years, while an annual average of 106,000 soldiers were not tested at all. Officials said that regular testing is even more difficult in the war zone because the testing facilities are often far away.

The cases reflect a broad range of incidents, describing accidental overdoses as well as soldiers buying drugs from Afghan troops, stealing morphine from medical aid bags or, in some cases, taking steroids, using drugs prescribed to someone else or taking medications long after their prescriptions had expired.

In one overdose case, a member of the Kentucky National Guard was found dead of “acute heroin toxicity” at his Afghanistan base after a soldier, also in the Kentucky Guard, bought heroin from a civilian contractor and used it with him. The report found that he also had morphine and codeine in his system.

Others more often involved soldiers who were found dead and were later determined to have taken a mix of prescription and other opiate drugs.

The nonlethal cases range from a soldier failing a random drug test to more organized abuse.

In one case, seven members of the 3rd Brigade, 10th Mountain Division were found to have smoked hashish and/or ingested heroin numerous times, including some bought from members of the Afghan Army and police. The investigation found that one other brigade soldier acted as a lookout while others used the drugs.

Opium is a key revenue source in Afghanistan, both for the farmers and the insurgency, which can make money selling, transporting or processing the drugs. According to a U.N. report, revenue from opium production in Afghanistan soared by 133 percent in 2011, to about $1.4 billion, or about one-tenth of the country’s GDP.