Three new packs of endangered gray wolves are roaming the northernmost tier of California, officials said this week, delighting conservationists but worrying ranchers and others who say the rapidly returning predators threaten livestock, pets and people.

The new packs, spotted in Shasta, Tehama and Lassen counties, bring the total in the state to 10, the California Department of Fish and Wildlife said Tuesday. Because each is led by a mated pair, the new Ashpan, Ishi and Tunnison packs could contribute to the state’s growing wolf population, now estimated at up to 70 animals.

“How wonderful to witness another year of continued growth in California’s recovering wolf population,” Amaroq Weiss, a senior wolf advocate at the Center for Biological Diversity, said in a statement. “It’s inspiring to watch this renaissance, and we should do everything we can to ensure California’s wolves have every chance to thrive.”

Many Californians were fascinated when the first gray wolf, OR-7, crossed into California from Oregon in 2011, and watched eagerly as their numbers began to climb. The young male was the first wild wolf spotted in the state since 1924, when the animals were essentially hunted out of existence.

As their numbers increased, wolves began settling in Northern California ranchlands and mountain grazing areas. The resulting increase in attacks on calves has alarmed ranchers and cost the state millions to reimburse losses and support non-lethal deterrents.

Wolves in California’s north state counties killed 13 calves and injured seven more in April alone, state data show, sparking an outcry from ranchers who are barred from shooting wolves or using aggressive deterrents like drones. Four counties have declared states of emergency over wolf activity.

“We continue to have concerns that additional wolves mean additional depredation on livestock,” said Kirk Wilbur, a lobbyist for the California Cattlemen’s Association. While ranchers are not asking to be allowed to hunt wolves, the group is urging the state to delist wolves from the endangered species list, allowing them to be trapped, hazed or, in some cases, euthanized by wildlife officials.

Ranchers’ concerns about wolves became the backdrop earlier this month at a heated hearing on whether to increase protections for coyotes, which also can prey on cattle.

California’s wolves are listed as endangered at both the state and federal levels, making it illegal to kill them and restricting methods to harass or relocate them.

However, the growing population has prompted discussions about updating the state’s wolf management strategy to allow stronger protections for livestock and public safety.