BROWNSVILLE, Texas (AP) _ Five babies have been born this year without fully developed brains in a county where the condition has been unusually common for several years.

Cameron County's latest anencephalic baby was born last week, said Dr. Judy Henry, an epidemiologist with the Texas Department of Health in Austin.

''Seems like the numbers are going up again,'' she said. ''We may get as many this year as we did last year.''

Anencephalic babies are born missing all or part of their brains. They are either stillborn or die soon after birth. One such baby in Florida recently became the center of a controversy when a court refused to let her parents donate her organs to other infants before her death.

State and federal health agencies are investigating 20 cases of anencephaly and 10 cases of spina bifida, an anomaly of the spine, reported in Brownsville from 1989 through the end of 1991. A report is expected later this year.

Anencephaly occurs in two to three of every 10,000 births in the United States and three or four per 10,000 in Texas, according to the state. There were about a dozen anencephalic babies in Cameron County, which surrounds Brownsville, in roughly 8,000 births last year.

Investigators have said they have no idea what might be responsible for the anencephaly outbreaks. They are trying to discover links between the families that had the anencephalic children.

Scientists don't know what causes anencephaly. A 1990 study found that fathers routinely exposed to solvents were more likely to produce anencephalic babies, but didn't prove a cause and effect.