The National Guard is joining the search in Washington State for a man the police say killed his three young daughters.

More than a hundred law enforcement officers are combing parts of central and northern Washington State for the man, Travis Decker, who the police say has wilderness skills that could help him survive for weeks on his own.

The police say Mr. Decker kidnapped the three girls — Olivia Decker, 5; Evelyn, 8; and Paityn, 9 — on May 30. They were found dead on Monday near a campsite roughly 70 miles east of Seattle. Each child had a plastic bag over her head, according to an affidavit from the police in Wenatchee, Wash., where the girls lived with their mother.

Large swaths of wilderness around where the girls’ bodies were found have been closed to the public as the manhunt has intensified. The U.S. Forest Service closed some trails, roads and campsites in the Okanogan-Wenatchee National Forest. On Thursday, the National Park Service closed parts of the Lake Chelan National Recreation Area, a part of the North Cascades National Park Service Complex to the north of the national forest.

On Friday, Gov. Bob Ferguson pledged to support the investigation by sending National Guard resources and emergency funding.