A polar bear that killed a young mother and her baby in western Alaska was likely an older animal in poor physical condition.
However, tests came back negative for pathogens that affect the brain and cause aggressive behaviour, officials said.
Dr Kimberlee Beckmen, a state wildlife veterinarian, collected and examined samples from the bear’s head the day after the attack, when weather conditions allowed her and an Alaska State Trooper to fly to the village.
The results of her analysis, indicate the bear was an adult male, probably older and in poor physical health.
Officials sent a tooth to a lab to determine the bear’s age, but those results will not be known for months.
Standard tests conducted on available tissues for pathogens were negative for rabies, toxoplasmosis, distemper and bird flu.
“There is no definitive explanation as to why the bear was in poor body condition,” the Alaska Department of Fish and Game and the US Fish and Wildlife Service said in a joint statement.
Summer Myomick and her one-year-old son, Clyde Ongtowasruk, were mauled to death on January 17, as they left the school in Wales, Alaska, for a short walk of about 150 yards to the town’s medical clinic.
School employees attempted to stop the attack by hitting the bear with shovels, but it turned on them and chased forcing them back inside for safety.
The principal slammed the door to keep the bear out of the school, which was in session.
A village resident later arrived with a gun and killed the animal.
It was the first fatal polar bear attack in Alaska in three decades.
Polar bears are the largest bear species, according to the Fish and Wildlife Service. Males typically weigh 270-540kg, but can be more than 770kg and reach up to 10 feet in length.
Polar bears generally feed on seals but also prey on walruses and beluga whales.
Wales, a whaling village of about 160 people, is located about 640 miles north-west of Anchorage and is accessible by plane or boat.