"It is clear there is more work to do," Johnson said at news conference following his tour on Sunday.
Johnson, along with Federal Emergency Management Agency administrator Craig Fugate, visited the debris field left by the March 22 slide. Thirty people were killed and 13 remain missing after a hillside collapsed, causing a massive mudslide that wiped out the community of Oso, about 55 miles northeast of Seattle. The debris field of downed trees, shredded houses and flattened and twisted cars sprawls over hundreds of acres. The mudslide also destroyed a section of a rural state highway.
During the tour, Johnson also met with first responders, some of whom were the first on the scene.
"The community has come together in a profound way," the Homeland Security secretary said, according to The Seattle Times.
He urged residents affected by the slide to apply for FEMA aid. The agency reported that 190 people already have applied for assistance. Last Wednesday, President Barack Obama declared a major disaster to help state, tribal and local recovery efforts.
Johnson and Fugate were joined by Gov. Jay Inslee, U.S. Sens. Patty Murray and Maria Cantwell, Rep. Suzan DelBene and the mayors of the nearby affected towns of Arlington and Darrington.
"We were here shortly after the disaster occurred, we are here now, and we will continue to be here as the recovery goes on," Johnson said in a statement after the tour.
Meanwhile, search teams on Sunday continued the grueling work of combing through the debris field to look for victims as officials prepared for spring runoff that is expected to swell the nearby Stillaguamish River. The mudslide blocked parts of the river and caused upstream flooding.
The U.S. Army Corps of Engineers is preparing to build a berm - a rock and gravel barrier - in hopes of preventing the river from flooding parts of the debris field and state Highway 530. The exact location of the berm's placement has not been decided, but construction is expected to begin on Monday. The engineers are hopeful they can finish building the temporary berm in a week.
Amid the search, several victims of the mudslide were mourned by friends and family over the weekend.
On Sunday, a memorial was held for 21-year-old Alan M. Bejvl, who died in the slide along with his fiancee, Delaney Webb. The two were visiting her grandparents, Thom and Marcy Satterlee, when the slide came down, killing all four. The younger couple were planning a summer wedding at the Satterlees' property in Oso.