Still under fire for failing to check up on a pregnant Fort Bragg soldier who turned up dead, the Army defended its actions, saying there is no standard procedure for units to keep up with absent service members.

Spc. Megan Touma's company did not know where she was between June 12 and June 21, when her decomposing body was found in the bathtub of a Fayetteville, N.C., motel room. She was listed as AWOL — absent without leave — when she missed a scheduled military exercise.

Army spokesman Tom McCollum told The Fayetteville Observer that not all units keep track of soldiers the same way.

Touma, who was 23 and about seven months pregnant, transferred from the U.S. Army Dental Clinic in Bamberg, Germany, and had been assigned to the 19th Replacement Company, a "holding" unit for soldiers at Fort Bragg.

McCollum would not answer questions about the 19th Replacement Company's procedures, saying they are part of the Army's investigation into Touma's death.

Her death is being treated as a homicide, but no arrests have been made.

Touma was reportedly on her way to visit her fiance, a soldier stationed at Ft. Bragg, who is believed to be the father of her unborn child.

Also, police were investigating whether Touma fell victim to a possible Zodiac killer copycat.

A symbol similar to one often left by the nefarious Zodiac serial killer of the 1960s was scrawled in lipstick on a mirror in the North Carolina hotel room where Touma was found, according to detectives.

A letter sent to a local newspaper and published last week also contained the symbol, a circle with a cross through it.

"I will start using my role-model's signature," wrote the author of the letter, which was posted on the Web site of the Fayetteville Observer.

The Zodiac killer was blamed for at least five slayings in California in the late 1960s but never caught.

Police questioned the letter's credibility, and believe the author's claim of being a serial killer was an attempt to mislead investigators and the media.

The Army's criminal investigations unit joined the effort to catch Touma's killer; a second autopsy will be performed.

The Associated Press contributed to this report.