Ansar al-Suna, an al-Qaeda-linked terror organization, claimed responsibility for the fire and said the rockets possessed a double warhead.
The organization says the fire was retaliation for attacks on female Palestinian inmates in Israeli prisons. "A number of (female) inmates have fallen victim to indecent assault by the wardens," it stated, adding that it would continue to attack Israel.
The investigation was launched following a complaint filed by the inmate, which claimed that the warden had abused her. The suspect has denied the allegations.
Ali Waked contibuted to this report