KUALA LUMPUR, Malaysia (Reuters) - Ten endangered Borneo pygmy elephants found dead in a Malaysian rainforest in recent weeks may have been poisoned by something they ate, wildlife officials said on Tuesday.

Four elephants were first reported dead on January 23 and another four were found dead two days later in the Gunung Rara Forest Reserve, located in Malaysia's Sabah state on Borneo Island.

The eight dead elephants were suspected to be linked with "two highly decomposed elephant carcasses" found earlier this year, said Laurentius Ambu, director of the Sabah Wildlife Department.

A department veterinarian said no obvious external injuries were found on the animals, but they suffered from severe hemorrhages and ulceration of the gastrointestinal tract.

"We highly suspect that it might be some form of acute poisoning from something that they had eaten, but we are still waiting for the laboratory results of the chemical analysis from samples taken from the dead elephants to confirm the diagnosis," senior veterinarian Sen Nathan said in a statement.

Seven of the dead elephants were females and three were males, ranging from 4 years old to around 20, the statement said.

The World Wildlife Fund (WWF) estimates there are fewer than 1,500 Borneo pygmy elephants found in the wild, with most of them residing in Sabah state. The elephant is smaller than other Asian elephants and their African relatives with larger ears and a gentle nature.

Officials declined to make further comment while the incidents were still under investigation by a special force set up to determine the cause of the deaths.

(Reporting by Angie Teo in Kuala Lumpur; Editing by Colleen Jenkins and Alden Bentley)