ANCHORAGE, Alaska — A rescued polar bear cub is thriving at the Alaska Zoo but federal wildlife officials said Wednesday they briefly considered trying to reunite the wild tyke with its mother after the adult bear was spotted on sea ice of the state's northern coast.

U.S. Fish and Wildlife officials ultimately concluded it was unclear whether the mother bear would re-accept the small cub after walking more than 30 miles away onto sea ice.

The cub remains at the Alaska Zoo in Anchorage, where it has grown from 17 pounds to 30 pounds. The bear will remain at the Alaska Zoo until another zoo home is found.

The cub, its sibling and its mother were captured April 15 by a U.S. Geological Survey research team. The cub weighed 19 pounds. Researchers placed a radio collar on the mother and tags on the cubs' ears.

On April 26, employees of ConocoPhillips called the U.S. Fish and Wildlife Service and said a lone polar bear cub had been spotted north of an ice road. The oil company restricted traffic along the road and was asked to see if the sow showed up.

The cub was monitored until 1 a.m. the next day, when coastal fog rolled in. The mother bear has not been seen.

When fog lifted at noon, neither the cub nor its mother could be found.

Late April 28, the cub was finally spotted again, alone, on a ConocoPhillips drilling pad four miles south of its location along the ice road. Wildlife officials concluded the cub had no chance of surviving on its own and likely would not reunite with its mother. The cub was captured at 1 a.m. April 29. It weighed just 17 pounds. It was flown to Anchorage that night.

The ear tag confirmed the cub had been captured but its mother had slipped out of the radio collar. The cub weighed 17 pounds, two pounds less than it had when captured April 15.

However, a day later, the USGS research crew spotted the adult female, identified by a paint mark, with her other cub on sea ice roughly 30 miles from the abandoned cub.

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Agency officials considered whether to reunite the cub with the mother but ultimately decided no.

Agency officials said they were not certain that the adult female could be found again and that additional stresses would be placed on her and the remaining cub if she were re-captured, which would be necessary for uniting the bears. It also was unclear whether the mother would re-accept the cub.

They also concluded that the orphaned cub, already been moved from its natural environment to Anchorage, may not have survived because her weight had dropped to 15 pounds.