Five children and an adult drowned at a summer camp in southern Russia on Wednesday, a spokesman for the regional investigation department said.
A spokesman for the regional emergencies ministry said rescuers were looking for a sixth child.
"There are six victims - a camp counselor and five children, three girls and two boys," the investigators' spokesperson said.
The victims were part of a group of 63 children and seven adults from Moscow who were staying at the Azov summer camp. The six bodies were found by rescuers, while one child was found alive and taken to an intensive care unit and another child is still unaccounted for.
More than 50 people were involved in rescue efforts.
The incident took place early on Wednesday, when the group went on a boat trip to an island in the Sea of Azov, Russian prosecutors said. During the trip, the children were allowed to swim in the sea in the area with undeveloped shoreline and no rescue facilities.
A spokesman for the regional emergencies ministry department said the children were caught in a strong underwater current.
"The children were being carried away by the current, and one of the camp counselors rushed to help," an emergencies ministry source said.
Russia's first deputy emergencies minister, Ruslan Tsalikov, said the tragedy was caused by "carelessness and noncompliance with elementary safety rules".
A criminal investigation has been launched.
President Dmitry Medvedev instructed Prosecutor General Yury Chaika to carry out an inspection in the camp. The local authorities have been instructed to help relatives of the deceased.
Russia's ombudsman for children's rights said he would visit the camp next week to look into the fatal incident.
"We will look into the situation. The circumstances surrounding the children's deaths should be investigated. We should also check how well the camp was prepared to accept children," Pavel Astakhov said.
Emergency Situations Ministry figures show accidents on water as the third highest cause of accidental death, after fires and traffic accidents. According to the ministry, 6,855 accidents on water were recorded last year, in which 6,476 people died.
