New Zealand’s ban on semi-automatic weapons took full effect Saturday, more than nine months since a shooting spree in Christchurch caused the country to enact sweeping gun reform.

A six-month window to turn over high-powered firearms outlawed following the armed rampage that killed dozens of worshipers at two mosques in Christchurch ended at midnight Dec. 20.

Going forward, Kiwis caught possessing those weapons risk facing consequences ranging from losing their gun permits to imprisonment, said New Zealand’s minister of police.

“Police are now preparing to follow up firearms [license] holders who are known to still hold prohibited guns,” Stuart Nash said in a statement. “My strong advice to these people is to voluntarily surrender them or face risk of prosecution, loss of [license] and firearms, and five years jail.”

New Zealand moved to outlaw most semi-automatic weapons, large-capacity magazines and some shotguns after 51 people were killed during the March 15 massacre in Christchurch.

“Our gun laws will change,” Prime Minister Jacinda Ardern promised soon after the shooting spree.

Subsequent reforms have resulted in around 60,907 prohibited firearms being either removed from circulation or pending collection, Mr. Nash said Saturday. The vast majority — 56,250 — were handed in during a buyback and amnesty program started in June, the likes of which resulted in the country paying out approximately $102.2 million in New Zealand dollars, or around $67 million U.S.

Around 33,000 firearm owners participated in the monthslong gun buy-back program, according to the New Zealand minister of police.

“We acknowledge this has been a difficult process for some people and we want to thank all of those firearms owners that have taken part in the Amnesty & Buy-back process,” Mike Clement, deputy commissioner of New Zealand Police, said in a statement.

Brenton Tarrant, an Australian, has been charged with dozens of counts of murder and attempted murder in connection with the Christchurch massacre. He has pleaded not guilty.