A Hamas security source said Thursday investigations indicated that three people from the Gaza Strip were involved in the deadly attack against Egyptian soldiers earlier this month in the Sinai Peninsula.

The three Palestinians are members of extremist Salafi groups and their whereabouts are unknown, the source said.

"Their involvement in the attack was marginal and it is no more than providing technical help," the sources said, adding that most of the assailants were Egyptians and other nationals.

It is the first time that Hamas, which governs Gaza, admits that people from the territory that borders Egypt took part in the Aug. 5 attack, in which 16 Egyptian soldiers were killed.

Egypt shut down Rafah crossing point between Gaza and Egypt after the attack, making the departure restricted to humanitarian cases.