THURSDAY, April 23 (HealthDay News) -- Seven people in California and Texas have now been diagnosed with a unique form of swine flu, U.S. health officials said Thursday.

All seven people have recovered, Dr. Anne Schuchat, director of the U.S. Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases, said during an afternoon teleconference. "So far this is not looking like a very severe influenza," she said.

The patients -- three females and four males -- range in age from 9 to 54, Schuchat said.

The first two cases were reported Tuesday in California. There are now five cases in California, including the father of one of the original patients. The other two cases are near San Antonio, Texas, Schuchat said.

"At this point we don't know the extent of the spread of this strain of human influenza derived from swine," she said. "We don't know exactly how people got the virus. None of the patients have had direct contact with pigs."

ATLANTA — Health officials are investigating a never-before-seen form of the flu that combines pig, bird and human viruses and which has infected seven people in California and Texas. All the victims recovered, but the cases are a growing medical mystery because it's unclear how they caught the virus.

Army criminal investigators are looking into the possibility that disease samples are missing from biolabs at Fort Detrick.

As first reported in today's edition of The Frederick News-Post by columnist Katherine Heerbrandt, the investigators are from the U.S. Army Criminal Investigation Division unit at Fort Meade.