A mother bear and her three cubs were rescued after becoming trapped inside a large water storage tank in La Verne Saturday, prompting a large response from firefighters and wildlife officials.

Officials said the bears were in distress for hours before one of the cubs managed to escape on its own.

First responders dubbed the effort "Operation Care Bear" after the bears spent more than 12 hours inside the tank. The rescue happened near Claremont Wilderness Park's 5-Mile Loop Trail.

Firefighters shared video of the rescue, which ended with three bears emerging from the tank. The bears had apparently squeezed through a 1-foot-wide opening in the concrete structure and became trapped inside.

Crews used a saw to cut a larger hole in the tank and lowered a ladder to help the animals escape.

"They were exhausted, so it took a few minutes for the first cub to come out, then the second cub got out, and then finally the mother," said Keith Navarre with the Los Angeles County Fire Department.

The bears were spotted around 8 a.m. Saturday by Glendora residents Eric McDonald and Jamie Kirk.

"We climbed up top, and there's a small hole and right away we see a bear staring at us, kind of holding on to the walls because it was full of water," Kirk said.

McDonald said he and Kirk were concerned about the animals' condition.

"We were just concerned that, certainly they had water, but they would get hungry and there's no telling how long they'd been in there," he said.

Tyler Christensen and Bradney Boli also encountered the bears and recorded video of the bears inside the tank.

"I just stuck my head in the hole. One was all tucked up on the top. There's like a little pole. They were just scared to death," Christensen said.

"I think the bears got very lucky because it would not be easy to hear that," Boli said.

California Department of Fish and Wildlife drained water from the tank before firefighters from La Verne and Los Angeles County assisted in the rescue. The bears may have been seeking water during the hot and humid weather.

One of the three cubs escaped the tank before rescuers arrived. That cub has since been reunited with its family.