Minnesota officials announced Thursday that lead fragments, apparently from lead bullets, have been found in 25 percent of venison samples collected from Minnesota food shelves.

The discovery has potential ramifications for Minnesota's half-million deer hunters and their families, and could affect management of the state's 1.3 million deer herd.

But officials said they don't know whether the problem is widespread and can't advise hunters whether their venison is safe to eat. Last fall, firearms hunters killed about 224,000 deer.

"We didn't issue a broad statewide recommendation to all hunters because we don't have enough information to tell hunters one way or the other," said Dan Symonik, Minnesota Department of Health lead poisoning prevention program supervisor.

Food shelves were told to destroy remaining venison and consumers who already have received the frozen meat were told to discard it. More venison will be tested.

Department of Natural Resources Commissioner Mark Holsten said his agency will work with the state Health and Agriculture departments to develop meat-processing guidelines.

"As to the immediate concern of the venison they have in their freezer, they'll have to use their best judgment," Holsten said.

Hunters help keep the state's deer herd in check, and the DNR in recent years has liberalized regulations to encourage hunters to kill more animals to reduce their numbers.

It's too soon to know if the discovery of lead in some venison will affect hunter numbers or deer harvest, Holsten said.

"It's going to change our world a little bit; to what degree, we don't know," he said.

Symonik said the risk "depends on how much control a hunter has had over the processing and handling of that meat."

Holsten plans to continue to eat venison in his freezer because he's confident he butchered it properly.

The discovery of varying amounts of lead in 25 percent of the 299 samples tested surprised Minnesota officials because, until recently, it had never been an issue.

Last month, North Dakota found lead fragments in donated venison there and ordered it thrown away. That sparked the Minnesota investigation. Wisconsin also is testing donated venison. Iowa tested some and found trace amounts of lead.

Mark Johnson, executive director of the Minnesota Deer Hunters Association, called the discovery shocking and disturbing. "Let's slow down and figure out what's going on," he said.

Rick Watson, vice president and director of international programs for the Peregrine Fund, based in Boise, Idaho, that promotes the conservation of birds of prey, says lead bullets fired by high-powered rifles are the problem.

"It fragments, and the fragmentation can carry bits of lead fairly far [from the wound], farther than people expect," he said.

Birds such as eagles, condors and falcons get lead poisoning from eating entrails and animals killed by hunters, he said.

The solution, he said, is for hunters to switch to copper bullets. "They don't fragment," he said. Despite recent developments of bullets made of copper, lead remains the industry standard.

No reports of illness associated with the venison have been made.

In Minnesota, the venison was donated by hunters as part of a program that pays processing costs to encourage hunters to donate deer.

Of lead fragments found in the venison samples, the amount varied from 0.185 milligrams to 46.3 milligrams.

Because food shelves often serve children and pregnant women -- who are most at-risk for lead poisoning -- state officials told food shelves to dispose of the meat.

The samples came from a Bemidji processor and distribution centers in Duluth and Rochester.

The program has distributed nearly 78,000 pounds of venison to 97 food shelves. As of April 8, the food shelves had roughly 12,000 pounds of venison remaining.

Samples were X-rayed at a commercial food inspection company and the Agriculture Department conducted lead analysis. The tests examined ground venison and whole cuts.

Results varied according to the type of venison and where it was collected. The tests found the lead fragments were not uniformly distributed in the meat.

Symonik said the exact level at which health impacts occur from lead can depend on a variety of factors. While high-level lead poisoning can be fatal, the symptoms of low-level lead consumption may not be obvious.

"We don't have enough information or samples to make broad conclusions yet, but based on the available data it appears there is a chance someone could get a harmful dose of lead by eating this product," Health Commissioner Dr. Sanne Magnan said in a statement.

Most adults can tolerate small amounts of lead exposure without noticeable symptoms.

The DNR's Holsten said he's hopeful that, with some changes, the venison donation program can continue next fall. "There are no plans to abandon the program at this time," he said.

Meanwhile, Larry Keane of the National Shooting Sports Foundation -- the trade association for the shooting, hunting and firearms industry -- said Minnesota and North Dakota have overreacted.

"It remains the case that there are no scientific studies that establish a possible human health risk from consuming venison -- or other big game -- harvested using traditional ammunition," Keane said.

"We continue to believe the decision to take high-quality protein out of the mouths of the needy based on the information presently available is an over reaction."