LOS ANGELES (AP) — Prosecutors moved to drop charges Tuesday against a Southern California man arrested on suspicion of having explosives after a blast killed his former girlfriend at her day spa.

Court papers filed in U.S. District Court said material found during a search of Stephen Beal's house in Long Beach may not meet the criteria to be considered a "destructive device."

Beal was arrested during the investigation of the bombing that killed Ildiko Krajnyak on May 15 in her Orange County spa, but he was never named as a suspect in the blast.

Beal, a model rocket hobbyist, told investigators he had not made any bombs and did not have material for an explosion as powerful as the one he saw in news coverage.

Beal, 59, was charged with a single count of possessing an unregistered destructive device. Prosecutors asked the court to drop the charge.

Beal and Krajnyak had recently split up over issues of exclusivity and finances, he told investigators, according to an affidavit filed in court by an FBI agent. But they remained business partners.

Krajnyak, 48, was killed and two female clients were seriously injured when she opened a box that erupted in a fiery explosion at the spa in the city of Aliso Viejo, about 50 miles (81 kilometers) south of Los Angeles, investigators said.

Krajnyak, a mother and a licensed cosmetologist, had just returned to California after visiting family in her native Hungary.

Investigators said they found two improvised explosive devices, three firearms and more than 100 pounds (45 kilograms) of explosive material in Beal's house.

Beal's son speculated at the time of the arrest that investigators had discovered rocket-making materials.

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Associated Press writer Michael Balsamo contributed to this report.