Accidental release of an arsenic compound at a Hewlett-Packard Co. manufacturing facility in north San Jose injured five workers, fire officials said. Five production workers at the plant were overcome by fumes released by a malfunctioning gallium arsenide reactor, officials said. Four victims were treated at a hospital and released, a company spokeswoman said. Another worker was treated at the scene. Gallium arsenide, a mixture of gallium and arsenic, is used in the production of light-emitting diodes (LEDs), the spokeswoman said. LEDs are the illuminated digital readouts on clock radios, other electronic appliances and automobile instrument panels.