Fort Belvoir officials will begin testing approximately 1,000 children next week for possible lead poisoning after discovering dangerously high levels of lead in paint samples taken from base housing at the sprawling Army base in southern Fairfax County, military officials said yesterday.

Parents were informed of the potentially dangerous situation in a letter that was hand-delivered Monday to residents of the 446 apartments in the Lewis Heights area of the base.

Many of the parents were angered, telling a reporter they are worried that Army officials may have waited too long to inform them that their children may have ingested the lead-based paint.

In its mildest form, lead poisoning from paint can cause anemia and sluggishness in young children. Prolonged exposure can lead to learning disabilities and mental retardation.

"We're upset because it's out of our hands," said James Howard, who lives with his wife and two young daughters on the second floor of one of the two-story, red-brick apartment buildings. "They wait until four years after I move in to tell me the lead-based paint they've been using is highly toxic . . . I just hope my kids are all right."

The medical testing, which will be conducted over a three-day period next week, is believed to be one of the largest lead testings in a single area in Virginia in recent years. This year, state health officials say, about 2,600 youngsters throughout Virginia have been screened for possible lead contamination.

Fort Belvoir spokesman Jerry Childress said yesterday that "absolutely no cases" of lead poisoning have been reported to base medical personnel. He said next week's massive screening effort is "one step in good preventive medicine."

Childress said the Army also has begun repainting the hallways of all of the 26-year-old apartment buildings in the Lewis Heights enlisted personnel housing area. He said there is no evidence that the walls of the apartments themselves, which are repainted frequently, have lead-based paint.

Lead poisoning, frequently labeled the "silent epidemic" by medical experts who say it can go undetected in young children during its early stages, has gained nationwide attention as a serious health threat. Lead-based paint is considered harmful if swallowed, and medical experts say young children frequently may eat chips of flaking paint or can ingest the material by running their fingers along the walls then putting them in their mouths.

The six-paragraph letter handed to parents in the Lewis Heights area Monday began: "Recently samples of paint taken from hallway walls in Lewis Heights housing showed a large amount of lead. The amount of lead exceeds the maximum allowable in dwellings."

Army spokesman Childress said one of the paint samples contained a lead level of 1.9 percent -- more than triple the maximum allowable level of .6 percent imposed by federal regulations more than a decade ago. The samples were taken from the common hallways in the apartments leading to basement storage areas, Childress said.

Fort Belvoir officials submitted two paint samples to the federal testing laboratory at Aberdeen Proving Ground in Maryland July 12 after receiving reports of flaking paint in some of the hallways, Childress said. The results were received by Army officials Oct. 11.

Medical personnel from the base hospital will make house calls to each of the apartments in Lewis Heights next Tuesday, Wednesday and Thursday, taking blood samples from all children between the ages of 6 months and 5 years, the letter said.

Lead poisoning is treatable with medication, although severe cases involving brain damage cannot be reversed.

"It upsets me," said Judy Barker, whose 15-month-old daughter will be screened. "But at least they're trying to do something to find out if the children are contaminated."

Denise Harrison, mother of a 6-year-old daughter and a 4-year-old son, was more critical: "It took them a long time to tell us. That paint has been falling for a long time."

Some medical experts involved in efforts to detect lead poisoning in children expressed surprise yesterday that the excessive levels of paint were found on a federal military base. The government has launched several major programs to rid federally owned buildings of lead-based paint.

"I'm sort of amazed you'd find that on a federal installation," said Dr. Frederick Green, vice president of Children's Hospital National Medical Center and a founder of the Committee for Lead, a Washington activist group.

Although federal regulations now limit the levels of lead allowed in paints, it does not require containment or elimination of paint that already has been applied in buildings. The most severe problems can occur, experts say, when several layers of paint begin peeling, exposing the older layers of paint with higher levels of lead.