GAZA, Sept. 23 (Xinhua) -- A tunnel under the borders between southern Gaza Strip and Egypt collapsed on Tuesday night, leaving six Palestinians missing under the tunnel's rubbles, witnesses and Hamas security sources said.

    Witnesses in the southern Gaza Strip town of Rafah said a mysterious huge explosion was heard in the area, adding that six people went into the tunnel under the borders with Egypt, and apparently went missing after the collapse.

    The Egyptian security forces and rescue teams have started to look for the missing people in the tunnel, according to security sources.

    Tunnels became a profitable business for Gaza Strip residents after Israel imposed a tight blockade on the enclave after Islamic Hamas movement took control of it in mid June last year.

    Different kinds of goods such as food products, clothes, shoes, medicine and raw materials are smuggled from Egypt into Gaza through 200 tunnels dug under the Egypt-Gaza borders.

    Unofficial figures said that 45 Palestinians have been killed while digging tunnels or smuggling goods from Egypt to Gaza through these tunnels since the beginning of 2008.

    Palestinian security sources accused Egypt of planting explosives in the tunnels and spreading poison gas inside the tunnels in a bid to prevent smuggling.

    Israel said that Palestinian militant groups, mainly Hamas, are using the tunnels to smuggle all kinds of weapons used in attacks against Israel.