The state has taken the unusual step of closing a popular spot to waterfowl hunting after shotgun shell fragments were found in a school yard, apparently because improvements in weapons and ammunition allowed them to travel farther than expected.

“It’s just designed better. People use steel shot as opposed to lead shot … and manufacturers have worked hard on perfected their product. It creates a situation where those shot patterns are traveling a further distance,” said Col. Kevin Jordan, head of law enforcement for New Hampshire Fish & Game. “It may be an over-reaction but we don’t want to take the risk.”

The closure affects a popular duck-hunting area around the Pow Wow River in Kingston that borders Great Pond. “This is a spot I would have bone hunting in, not given it a second thought,” said Jordan.

The shell fragments were found outside Sanborn Regional Middle and High School after the opening day of duck season on Oct. 2. Jordan said the school is some “700-some-odd” feet from the nearest hunting site. State law requires hunters to be at least 300 feet from a dwelling, trail or pathway.

“We don’t understand how that could reach that far … but we’re not going to take the risk,” said Jordan. “Then we’ve got to make a decision about what to do permanently.”

No one was hit and the shell fragments probably wouldn’t have caused an injury in any case, he said.

The move is allowed under Emergency Closure powers given to the Fish and Game Department under RSA 206:15a. Executive Director Scott Mason made the decision.

The ban runs from a bridge crossing the Pow Wow River and marsh area on Ball Road up to Great Pond, but does not include Great Pond itself. Fish and Game described the marsh as “quality habitat” for waterfowl.

A number of housing developments are adjacent to the marsh.