These parents didn’t know why their children had lead poisoning. An applesauce recall offered clues.

In the days and months leading up to the Food and Drug Administration’s nationwide recall of WanaBana apple cinnamon fruit puree in late October, a number of families found themselves frantically searching their homes for sources of lead, desperately trying to understand how their children had been exposed to the heavy metal.

“This was a mystery to us,” one parent wrote in an adverse event report received by the FDA on Nov. 6. The report was among several provided to NBC News in response to a Freedom of Information Act request. The agency redacted all personal information from the reports, which are submitted by the public about concerns about specific FDA-regulated products.

A routine well-child checkup on Oct. 11 uncovered that the child’s blood lead levels, which were within the normal range in the previous year, had spiked to 5.1 micrograms per deciliter — a level considered above what’s seen in most children, according to the Centers for Disease Control and Prevention.

“We have a newer home and all toys are new,” the parent wrote. “We keep our home clean and there are no hobby materials that could contain lead in the home.”

Then, later that month, WanaBana announced it was recalling its apple cinnamon fruit puree pouches due to elevated lead levels. The child, the parent wrote, had consumed three pouches of the puree the week before getting tested.

Confusion, frustration and alarm from parents were common in the reports received by the FDA about lead poisoning in children who were said to have consumed any of three recalled products — WanaBana apple cinnamon fruit puree, Schnucks applesauce pouches with cinnamon and Weis cinnamon applesauce. The Schnucks and Weis products are also made by WanaBana USA.

The FDA said last month that parents should not buy the products as it investigates cases of lead poisoning in children, reports of which the agency said it began receiving in mid-October.

As of last Tuesday, the agency had received at least 65 reports of lead poisoning in children potentially linked to the recalled products. All of the reported cases — which haven’t necessarily been verified or confirmed by the FDA — are in children under age 6.

Mariah Piazza, 27, of Buffalo, New York, told NBC News that she was among the parents who submitted a report to the FDA in November.

Her 1-year-old son, Caiden, had been eating the cinnamon applesauce pouches almost every day for about a month.

In March, a blood test revealed that Caiden had a blood lead level of 13 micrograms per deciliter. A home search from the New York State Health Department found nothing in the family’s home that could have caused the lead poisoning, she said. (The CDC recommends home checks for children with blood lead levels above 3.5 micrograms per deciliter to identify potential sources of lead.)

“It was a total surprise,” said Piazza, who added that the home investigators told her she may never know where the lead exposure came from.

Erring on the side of caution, she cut out all processed foods from Caiden’s diet, including the WanaBana pouches. It wasn’t until early November that she learned about the recall. She felt relieved.

When Caiden stopped eating the pouches, “his levels went down super fast,” she said. “Most people when their kid is lead-poisoned and they get tested, it takes almost a year for their levels to go undetectable.

No immediate symptoms

There is no known safe blood lead level in children, according to the CDC. The agency uses a level of 3.5 micrograms per deciliter to identify kids with higher blood lead levels than most.

Long-term exposure to lead, a neurotoxin, can cause damage to the nervous system and brain, said Dr. Adam Keating, a primary care pediatrician at the Cleveland Clinic. It can also cause ongoing learning and behavioral problems, as well as problems with hearing and speech.

What constitutes long-term exposure, however, remains unclear.

How long — and how much — lead exposure a child needs before they develop these issues is still an open question, said Dr. Cree Kachelski, a pediatric emergency medicine physician at the Mayo Clinic in Rochester, Minnesota.

Lead poisoning can be difficult to spot. Kachelski said that most children who have been exposed to lead are asymptomatic or have no obvious immediate symptoms.

“That’s why during the well-child visits, routine screening is done, because a large portion of children will just be asymptomatic,” she said.

In one report submitted to the FDA, a parent whose child had blood lead levels of 13 micrograms per deciliter said that their child had no symptoms, noting that they appeared “healthy at this time.”

In another report, a family wrote that their 1-year-old daughter had eaten the WanaBana apple cinnamon fruit puree pouches for nine months.

On June 1, a blood test at a primary care appointment revealed her lead levels were above average. A home search by the health department later found no obvious signs of lead in the family’s home, they wrote.

“After a month of trying to get the health department to come back out, the FDA released that the Wanabana Purée pouches had been recalled due to high lead content and our daughter had been consuming those over the last 9 months averaging 4-6 a week,” they wrote.

Some acute illnesses

A few of the reports described symptoms leading up to the blood tests.

One parent wrote in an adverse event report that they had purchased WanaBana apple cinnamon fruit puree for their 1-year-old son at Dollar Tree on Tuesday, Oct. 24.

The following day, a babysitter reported that the boy had lost his appetite, and by 5 a.m. on Thursday, he began vomiting. The parent immediately called the pediatrician, who advised the parent to watch the child over the weekend for signs of dehydration. The boy endured bouts of vomiting and diarrhea through the weekend, and the following Monday was diagnosed with stomach flu.

Unsure what caused the boy’s illness, the parent researched online and discovered the FDA’s recall of the WanaBana apple cinnamon pouches. Alarmed, the parent took their son to the hospital for lead testing and found that his levels were “above range.”

“I am concerned his flu-like symptoms were from the lead exposure in this recalled product,” the parent wrote.

Another parent said in an adverse event report that their 1-year-old son was found to be “severely anemic” during an annual checkup in early October.

The boy, who had been consuming the cinnamon applesauce pouches two to three times per day and “loved” the brand, had also been experiencing loose stool.

“The loose stools (initially thought was caused by breast milk) turned into explosive diarrhea that smelled like death,” the parent wrote.

Kachelski said gastrointestinal symptoms or stomach problems can be an early sign of acute lead exposure in children.

“So like vomiting, or they just don’t feel good because it upsets their GI tract,” she said.

Physicians often see constipation more than diarrhea in these cases, she said. It’s also possible that lead poisoning can look similar to a stomach bug.