Fouad Saadeddin, the governor of Minya, a province in central Egypt, said seven people are still unaccounted for, while several security officials said at least 10 are missing.
"The current was so strong, so bodies could have drifted away from the site of the accident," he told Egyptian state-run television.
Saadeddin said the final death toll would not be known until after the completion of rescue efforts, which were suspended on Sunday once darkness fell.
MENA quoted him as saying a large number of passengers were trying to get on the ferry when a ramp linking it to the river bank collapsed.
Security officials said one of the boat's railings also collapsed, sending more people into the water.
Television footage showed dozens of local residents gathered at the site watching police divers search for survivors.