SPENCER, Ia. – The two high school athlete deaths in Iowa in the last two-plus weeks are far from the national norm.

Woodward-Granger junior basketball player Drew Jacobson and Spencer senior wrestler Austin Roberts collapsed during their respective activities Dec. 2 in Des Moines and Saturday in Spencer.

In its most recently released report, the National Center for Catastrophic Sports Injury Research, based out of the University of North Carolina at Chapel Hill, found four fatalities from high school winter sports nationwide in the 2012-13 school year.

Two were in basketball and one in wrestling, but all were considered “indirect fatalities,” which are considered to be caused by systemic failure (usually cardiac or respiratory) as a result of exertion and lack direct physical trauma.

Roberts, 18, was in the 220-pound championship match at Saturday’s Spencer Invitational when he couldn’t gather himself during injury timeout and required medical attention on the mat. He was transported to nearby Spencer Hospital, where he died later that night. His death was the first in-competition wrestling death in Iowa in recent memory.

“He has never had any warning signs,” Roberts’ father, Travis Roberts, told NBC News. “We don’t understand what happened.

“One minute he was competing for the championship and doing fine. The third period started and he just went down and never got back up.”

Clay County medical examiner’s office released a statement Monday declaring, “preliminary investigation points to a natural cause of death,” which would exclude non-natural causes like physical trauma, intoxication or other poisoning.

Jacobson, 16, was in basketball practice on Dec. 2 when he suffered heart failure and was flown to Mercy Medical Center in Des Moines, where he died on Dec. 7.

“It wasn’t the result of anything that happened at practice; he just essentially collapsed,” Woodward-Granger superintendent Brad Anderson said. “Obviously our coaches were first at the scene. They did everything in their training, absolutely everything possible to keep him stable at that point. We had Woodward first responders and police offers show up, and they took over the scene. At that point, they got Dallas County here and they handled it, according to their training.”

Neither Roberts (6-foot-4, 220 pounds) nor Jacobson (6-3, 230) had any related medical conditions or incidents, according to their families and coaches. To be eligible to participate, Iowa high school male athletes must pass a yearly physical conducted by a “physician and surgeon, osteopathic physician and surgeon, osteopath, qualified doctor of chiropractic, licensed physician’s assistant or advanced registered nurse practitioner,” the IHSAA rules state.

The National Federation for State High School Associations released a statement in October on sports safety following an eighth football-related fatality. None was reported in Iowa.

“Despite all of these efforts on the part of the NFHS, its member state associations and the 19,000-plus high schools across the country to reduce the change for serious injury or death, there remains a risk involved in playing high school sports,” the release said. “With 1.1 million students playing a full-contact, collision sport such as football, there is a degree of risk involved.

“We wish we would not have to report another death in high school sports. That goal starts with continuing our efforts to minimize risk for the 12 million participants in high school activity programs.”

In May, 15-year-old Zacharie Schaubhut of Ankeny died playing pickup baseball in Bemidji, Minnesota, when a ball he pitched struck him after being hit.