Four giant cranes arrived Friday in the scene to help pull up the sunken ferry in Jindo, South Jeolla Province, officials said.

Three massive cranes were on standby at the scene until another crane arrived in the afternoon. 

The salvage operation to pull the ferry out of the waters will not be carried out without the consent of the families of the missing people, officials said. Any mishandling of the ship could lead to a loss of oxygen, which is critical for potential survivors, they added. 

The maritime authorities said that the salvage work might take up to two months.

By Lee Hyun-jeong (rene@heraldcorp.com)