The Army's top doctor, noting the drug overdose death of actor Heath Ledger, said Thursday the military is investigating a series of suspected similar deaths among wounded and injured soldiers.

Lt. Gen. Eric B. Schoomaker, the Army's surgeon general, said there has been "a series, a sequence of deaths" in the new, so-called "warrior transition units." Those are special units set up last year to give sick, injured and war-wounded troops coordinated medical care, financial advice, legal help and other services as they transition toward either a return to uniform or back into civilian life.

Without giving a number, Schoomaker said the deaths among the convalescing troops were "accidental deaths, we believe, often as a consequence of the use of multiple prescription and nonprescription medicines and alcohol."

"This isn't restricted to the military, alone, as we all saw the unfortunate death of one of our leading actors recently," Schoomaker told Pentagon reporters.

The New York medical examiner announced Wednesday that Ledger, the 28-year-old "Brokeback Mountain" star, died Jan. 22 from an accidental overdose the effects of taking six types of painkillers and sedatives.

Schoomaker said he didn't know whether the number of overdoses among soldiers was on the rise, but would try to provide statistics as soon as possible. The series of deaths was noticed and is getting attention partly because the new units concentrate the Army's temporarily disabled and ill into special groups, thus making it possible for leaders to track and tabulate their health issues more closely and carefully than ever before.

"We're dealing now with a group of wounded, ill or injured soldiers that have available to them through the medical system, a constellation of very potent and potentially lethal drugs (when taken) in the wrong combination," Schoomaker said.

He said a special team of pharmacists and other military officials will meet within days on the subject.

Officials are working to try to prevent such deaths and "alert the soldiers themselves about what the medications they have may do to them," Schoomaker said.

Officials want to "put a safety net around those folks who might have either psychological problems or other injuries or illnesses which may make it difficult to manage a constellation of drugs," he said.

"I don't believe those are suicides in the conventional sense. I think these are truly accidental deaths," he said.

Schoomaker brought up the subject of overdoses when asked how he assessed recent preliminary figures indicating a possible rise in Army suicides during 2007.

The figures showed that, as of last month, officials had confirmed 89 suicides last year among active duty and activated National Guard and Reserve - and that another 32 deaths were still under investigation. If all are confirmed, the total of 121 would be nearly a 20 percent increase over 2006.

Soldiers who have killed themselves most commonly have used weapons, not drug overdoses, which accounted for less than 10 percent of suicides in recent years, according to Army figures.

Statistics show accidental overdoses have become a national problem, with the deaths from accidental ingestion of multiple prescription drugs now exceeding deaths from illegal drugs, Schoomaker said.

He was holding a press briefing to talk about the warrior in transition units - three dozen units from which the military now oversees the care of nearly 9,800 outpatient soldiers. That includes nearly 1,400 with battle related injuries and about 8,400 with diseases and non-battle injuries.

The Army said approximately 43 percent of them have never been deployed to either the war in Iraq or Afghanistan, noting some have been injured in training, deployments to other places and so on.

Schoomaker said the units are part of a fundamental change the Army has made in its medical system since shoddy outpatient housing and bureaucratic delays were exposed last year at the Walter Reed Army Medical Center.

Officials have given greater priority to improving facilities for troops, increasing medical staffing and working with families of disabled soldiers. They have coordinated efforts with the Veterans Administration, for instance reducing by half some of the paperwork needed to get troops their benefits, said Brig. Gen. Michael Tucker, assistant Army surgeon general for transition care.

"It's been about a year since news reports brought to our attention some serious deficiencies in how we support our outpatient wounded, ill and injured warriors and our families," Schoomaker said. "In a little less that a year, we have made a major revision to our approach to our care of these soldiers and support of their families."