The rescue operation to free four adults and three teenagers who have been stranded in the Duhlata cave in western Bulgaria for two days, ended successfully late on Sunday.

The accident occurred after Saturday torrential rains and rising underground waters flooded the cave's lower passages.

The rescue teams have worked all through the night using heavy equipment such as excavators. The head of the operation told Darik radio he was optimistic regarding the outcome, adding this could be an unprecedented rescue effort in Bulgaria over its large scale.

The four adults are believed to be experienced in speleology with over 20 years of practice and to have all basics to survive inside, along with the teenagers, for several days. Rescuers further said the stranded people are in a safe part of the cave.

Nevertheless, Civil Defense pointed out it is reckless to not watch the weather forecast before undertaking such adventures.

The seven people entered the cave at about 8 pm Friday night. The kids are aged 11, 13 and 14, and are known to be teenage climbers. They are from Sofia, Pernik, and Karlovo.

The Duhlata cave is long 18 km and is known as the more complex underground labyrinth in Bulgaria; it has seven levels. It is near the village of Bosnek, alongside the Struma River.

The cave is secured with a door of metal bars but the speleologists received the key for the door from the mayor of the nearby village, not expecting that the torrential rains will affect their trip.