An investigation has begun into the death of a female elephant which collapsed and died at the roadside while carrying tourists to an ancient Cambodian temple.

Sambo the elephant collapsed of a fatal heart attack after ferrying two tourists - one at a time - to a temple in the famous Angkor Wat complex.

She had been working for 40 minutes in scorching heat that had reached 40 degrees - and a veterinarian concluded that she had died of a heart attack ‘due to high temperatures, heat exhaustion and lack of wind that would have helped to cool her.’

Tragic: Sembo the elephant died after working for 40 minutes in 40 degree heat, carrying tourists in Cambodia

Now animal lovers are demanding an investigation as to why the elephant, aged between 40 and 45 years, was forced to continue carrying tourists when the temperatures were so high and there was no wind.

Rambo had worked for the Angkor Elephant Company since 2001, said manager Oan Kiri, adding: ‘We’re all very sad to have lost her.’

A Facebook post - by user Yem Senok - carrying photos of the elephant lying dead on the ground has been shared more than 8,000 times.

A petition calling for the end of elephant riding to the famous temples has already gathered more than 10,000 signatures.

Worked to death: A veterinarian concluded that Sembo had died of a heart attack ‘due to high temperatures, heat exhaustion and lack of wind’

The elephant had carried tourists to the famous Angkor Wat temple complex in the scorching heat

Campaign: Shortly after the death of the 45-year-old elephant went public, thousands signed a petition to stop elephant rides in the area

Briton Jack Highwood, who runs the Elephant Valley Project, designed to protect Cambodia’s elephants, has called for regulated working conditions.

He pointed out that the Angkor Elephant Company had 13 remaining animals, which represents the largest concentration of captive elephants in the country.

‘Conditions should be regulated,’ he said, ‘if working Cambodia’s last remaining elephants is what Cambodia actually wants to do.’

The nationalities of the tourists who were carried by the elephant to the temple complex has not been revealed.

But a number of visitors who saw her lying dead at the roadside are reported to have wept.