By Jonathan Kent BBC, Kuala Lumpur

Animal welfare sources said the deaths were both easily avoidable and a damning indictment of the country's failure to take protection of rare species seriously.

Animal welfare experts said conditions were unsanitary

Malaysia has one of the most diverse and fragile ecosystems in the world and the Sumatran rhino is one of its rarest species.

Only 300 survive in the wild anywhere - around 100 of them in Malaysia.

A week ago the last of seven Sumatran rhinos at the country's only captive breeding centre died - the fifth death in a month and a major blow to conservation efforts.

Now animal welfare experts with a close knowledge of the centre have told the BBC they died from neglect.

Conditions at the centre were unsanitary - food and faeces were left to rot; cockroaches and rats, potential carriers of disease, were commonly found there, they said.

When the rhinos fell sick, laboratory staff were on holiday.

By the time urgently needed test results arrived, the rhinos were dead.

Other sources confirmed that those tests showed e.coli bacteria were found in the rhinos, but warned against concluding this was the cause of death.

However conservationists say this confirms the animals were being kept in poor conditions.

The whole notion of a captive breeding programme has now been called into doubt, with many experts saying the animals would survive better in the wild.