Authorities have found a second homemade explosive and more of a type of explosive previously discovered in a house in an unincorporated area near Escondido, California, officials said Thursday.

The house occupied by George Djura Jakubec, a computer software consultant who is now under arrest, has been described by authorities as a bomb-making factory. They say it holds the largest cache of the two homemade explosives ever discovered in one spot in the United States.

San Diego County authorities confirmed Thursday they have found pentaerythritol tetranitrate, or PETN, a favorite of al Qaeda bomb-makers that is now the target of new U.S. airport body scans and pat downs.

They also found more hexamethylene triperoxide diamine, or HMTD, in a bottle inside the house, but the two types of homemade explosives were not immediately removed because they are too volatile and the house is too cluttered to negotiate safely, Assistant Sheriff Ed Prendergast said.

Authorities had already recovered 8 or 9 pounds of HMTD, an explosive powder that suicide bombers use, authorities said.

The search of the house also turned up items “suggestive of armed robberies,” Prendergast said in a written statement.

In addition to bomb-making charges, Jakubec, 54, is charged with two bank robberies. Now being held in lieu of $5 million bail, he was on probation for a 2009 burglary conviction when he was arrested last week.

Authorities are investigating Jakubec’s intentions. He is a Serbian national who is a naturalized U.S. citizen, and he lived in the house with his wife.’

(Read More: CNN)