SEATTLE — Someone released an estimated 25,000 juvenile steelhead during an overnight break-in at a fish hatchery east of Seattle — and some are wondering if a disgruntled angler might be to blame.

Washington’s Department of Fish and Wildlife announced last month that it would not release hatchery steelhead into any Puget Sound rivers but one this spring, after a conservation group sued over the hatchery program.

While many anglers are happy to catch hatchery-raised steelhead, the Duvall-based Wild Fish Conservancy argued in U.S. District Court that the hatchery fish program had not been approved by federal officials under the Endangered Species Act, and that the hatchery fish hinder the recovery of wild steelhead.

The break-in at the Tokul Creek hatchery in eastern King County was discovered Tuesday morning, said Kelly Cunningham, a deputy assistant director at Fish and Wildlife. The ponds there were behind chain-link fence, barbed wire and a locked gate.

Someone cut the chains at the gate and pulled screens in a pond that was holding about 50,000 fish, he said. The screens had been blocking the fish from reaching Tokul Creek, a tributary of the Snoqualmie River, and about half the fish escaped.

“It is safe to say they are gone,” Cunningham said. “It would be virtually impossible to get them back.”

He declined to speculate on a motive, but said, “It’s no secret that it’s a highly polarized issue.”

In a statement, the Wild Fish Conservancy said it deplored the vandalism and is calling on federal fisheries officials to join the investigation.

“Besides state laws, the perpetrators also violated the Endangered Species Act,” the statement said, adding: “We also call on individual salmon and steelhead anglers, as well as the various Puget Sound angler organizations, to publicly condemn such activity.”

The state had been planning to release 900,000 steelhead from nine hatcheries into Puget Sound rivers this spring. After migrating out to sea, they would have returned to spawn — or be caught — in 2016 and 2017.

But the Wild Fish Conservancy raised legal objections, noting that since 1999, when Puget Sound salmon were first listed as threatened under the Endangered Species Act, the state had continued to raise and release hatchery fish without an evaluation by federal officials of how the hatchery fish affect wild salmon and steelhead. Research has shown that hatchery programs can hurt the genetics of wild fish and have bad ecological impacts as well, the group said.

The department agreed that research shows that some hatchery practices can hurt the productivity and recovery of wild fish. But it said it had made several changes to its program in the past decade in accordance with those findings.

Nevertheless, the state said that federal authorities never finished their review of the hatchery program, and without that approval, the department risked losing in court.

In a settlement in late March, the state agreed that it would not release any of the steelhead in Puget Sound rivers except for 185,000 on the Skykomish River. Instead, some of the fish were to be trucked to inland lakes in eastern Washington where they would not be able to reach Puget Sound rivers.