SEATTLE -

After touring the site of the deadly Washington mudslide, Department of Homeland Security secretary Jeh Johnson said federal help will continue until "this is done."

"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 Sunday. Thirty people were killed and 13 remain missing after a hillside collapsed March 22, 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.

He urged residents affected by the slide to apply for FEMA aid. The agency reported that 190 people already have applied for assistance. On 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

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.