(CNN) -- A San Diego County, California, contractor and San Marcos Fire Department crews began clearing brush, trees and wood fences Thursday near a house that authorities say is a "bomb factory" and the site of the nation's largest cache of homemade explosives ever found in one spot.
The clean-up marked the start of preparation to burn down the house in an unincorporated area near Escondido, California, that has been deemed too dangerous for bomb squads to re-enter, authorities said. The house contains two kinds of volative explosives, and the interior is too cluttered for bomb crews to negotiate safely, officials said.
Crews are building a 16-foot metal-frame wall to the north of the single-story suburban house to protect another house from radiant heat during the burn, planned for some time between December 8 and December 10, San Diego County Sheriff's spokeswoman Melissa Aquino said.
Attached to the frame is fire-resistant drywall, and fire crews will also apply a gel on the day of the burn, officials said.
Authorities installed on Tuesday a portable weather station on the roof of the Escondido Fire Department Fire Station No. 3 to obtain weather patterns for the day of the burn, officials said. Authorities will burn down the house when the skies are clear and the winds are slight at 5 mph out of the west, officials said.
The house's resident, George Djura Jakubec, 54, a computer software consultant, is being held in lieu of $5 million bail on bomb-making and bank robbery charges.
Bomb crews discovered two types of homemade explosives inside the house last week -- also the kind that terrorists worldwide favor: hexamethylene triperoxide diamine, or HMTD, and pentaerythritol tetranitrate, or PETN, which is now the target of new U.S. airport body scans and pat downs. Authorities didn't remove those explosives from the house.
Eight or 9 pounds of HMTD were found in the backyard after a gardener was injured when he accidentally ignited some of the material almost two weeks ago. One expert likened the 9 pounds to a large car bomb, which could blow out the house's windows and doors and damage adjacent houses.
Authorities are now investigating Jakubec's intentions.
The overwhelming clutter inside the house suggests Jakubec was a hoarder of papers, boxes and other items, officials said. Friction from moving any papers or boxes could cause hidden explosives to ignite, officials said.
Authorities told residents that the burn should destroy the explosives in a controlled manner, though some residents have expressed skepticism about the plan.