The number of American soldiers seeking treatment for opiate abuse has skyrocketed over the past five years, at a time when the U.S. military has been surging forces into the heart of the world's leading opium producer.

Pentagon statistics obtained by FoxNews.com show that the number of Army soldiers enrolled in Substance Abuse Program counseling for opiates has soared nearly 500 percent -- from 89 in 2004 to 529 last year. The number showed a steady increase almost every year in that time frame -- but it leaped 50 percent last year when the U.S. began surging troops into Afghanistan. Army troop levels in Afghanistan went from 14,000 as of the end of 2004 to 46,400 as of the end of 2009.

The Army did not break down the opiate-use data to show how many of the soldiers had been deployed to Afghanistan or what specific opiates they were using; opiate drugs include morphine, codeine and heroin.

Lt. Col. Christopher Garver, a U.S. Army spokesman, said the military has been monitoring the uptick and is "concerned about it." He said the numbers reflect use not only of heroin, but of prescription drugs, that the abuse may not be "directly correlated to previous deployments," and that the increase could reflect an increase in reporting abuse -- not just drug use itself.

But the abundance and accessibility of heroin in Afghanistan surely account for part of the jump, said Lt. Col. Tony Shaffer, an Army Reserve officer who served in Afghanistan from 2003 to 2004.

Shaffer said heroin abuse had "started to get out of hand" when he was in the country. He said a "black market" existed where troops on U.S. bases would trade goods to local Afghans in exchange for heroin.

"It sounds like it kind of went way beyond that," he said after learning about the statistics. "It's inevitable. ... It's available. It's right there."

Shaffer, who now works with the Center for Advanced Defense Studies, said the availability of the product combined with high stress levels from multiple tours of duty amounts to a dangerous mix that can lead to hard drug abuse.

As a potential measure of Army stress levels, suicides have steadily climbed in recent years. The Army reported there were 160 possible suicides among active-duty soldiers in 2009, up from 140 the year before.

The opiate-use statistics were first obtained by the watchdog group Judicial Watch, which requested them through a Freedom of Information Act inquiry and provided them to FoxNews.com. The Army confirmed the authenticity of the report.

Chris Farrell, director of investigation with Judicial Watch and a former Army intelligence officer, said he sought the data to see what kind of impact Afghanistan's locally produced drug supply may be having on U.S. troops.

"This whole situation detracts, obviously, from mission readiness," he said, noting that actual hard drug use is probably far higher than the numbers show. "It's a public interest issue."

David Rittgers, a former Special Forces officer who served in Afghanistan from 2002 to 2004, said he didn't see opiate abuse among U.S. forces while he was in the war zone, though it was "rampant" in the Afghan forces. But he said the abuse of drugs ranging from painkillers to heroin could also occur after soldiers return home from deployment and have trouble readjusting to life in the States.

"This is an outlet, just as alcohol abuse is an outlet," said Rittgers, who is a reserve JAG officer and clarified that he is not a Pentagon spokesman.

While the number of soldiers seeking treatment has risen dramatically, urinalysis drug tests in Afghanistan do not reflect the trend. According to the Army data, soldiers tested positive for heroin use just twice in the past three years.

Western forces have given mixed signals about how heavily they are targeting opium drug production in Afghanistan, a major source of funding for the Taliban. The DEA said last month that opium seizures rose 924 percent in 2009. But recent reports have said the military is focusing far more on fighting the Taliban than in cutting off the opium supply at the source.

While some say going after opium farming worsens relations between Western forces and the local population, others say eradication is critical.

Gen. Barry McCaffrey, the former U.S. drug czar, said during a speech to the National Association of Addiction Treatment Providers last year that the military risks exposing its troops to drug abuse problems if it doesn't destroy the opium crops.

"I'd be astonished if we don't see soldiers who find 10 kilograms of heroin and pack it up in a birthday cake and send it home to their mother with a note that says, 'Don't open this package until I'm home,'" he said, according to an article on the speech in the Palm Beach Post.