Mark Colvin: The wrong security force may be getting the blame for introducing cane toads into East Timor.

This week the Australian-led INTERFET force was accused of carrying hitch-hiking cane toads on equipment and trucks from Australia to Timor in 1999.

And an East Timorese environment group made new allegations today; it said the cane toads were first found in Timor near an Australian base in 1999 and that two locals died after mistaking the toads for edible river frogs.

But PM can now reveal that the species at the centre of the claims is a type of toad not found in Australia but common in Indonesia. Zoie Jones reports.

(sound of toad croaking)

Zoie Jones: That's the trademark mating call of the bufo marinus toad. It's the species that was introduced into Australian cane fields from South America in the 1930s.

The East Timorese environment group the Haburas Foundation has collected photos and what it says are eye-witness accounts of bufo marinus near the north-western border town of Batugade, where Australia's INTERFET troops had a base camp in 1999. The group has presented their findings to Timor's national parliament and their spokesman is Demetrio do Amaral de Carvalho.

Demetrio do Amaral de Carvalho: They found cane toads from '99 before they don't have that kind of species in that region. So it starts from '99.

Zoie Jones: Have you researched what kind of toad has been spotted in this north western coastal region?

Demetrio do Amaral de Carvalho: Yes. Yes.

Zoie Jones: Can you tell me which cane toad it is?

Demetrio do Amaral de Carvalho: Bufo Marinus.

Zoie Jones: That's the Australian toad?

Demetrio do Amaral de Carvalho: Yes, I think from our comparisons to the anatomy and morphology of the cane toad from Australia, we have concluded that there are similarities. Very, very similar.

Zoie Jones: In its report to the Timorese Government, the Haburas Foundation said that two people died; one in 2005 and one in 2006, after mistakenly eating the poisonous pests.

The foundation also says some East Timorese believe the ADF (Australian Defence Force) deliberately introduced cane toad eggs into swamps as a measure to combat malaria-carrying mosquitoes around the Batugade camp.

The Defence Department has strongly denied that claim. In a statement, a spokeswoman says the ADF used a biological insecticide in the swamps around Batugade, but that cane toads were never used.

The Department has also said that because of the high traffic into East Timor from 1999, it would be difficult to pin-point the source of any introduced species.

(sound of toad croaking)

Zoie Jones: One of the photos used as evidence by the Haburas Foundation of the bufo marinus toad being in East Timor shows a large toad that's being dangled by the legs, with its back clearly in view. Cane toad expert Professor Ric Shine from the University of Sydney says it's a case of mistaken identity.

Ric Shine: The toad in the photo is a black-spined toad Bufo elanostictus. It's a much smaller animal than the cane toad.

Otherwise it's broadly similar in shape and so on. The poisons are less toxic than those of the cane toad and there's not as much of them but again broadly, chemically, they're probably relatively similar.

Zoie Jones: For a lay person would it be easy to confuse the Australian cane toad and this black-spined cane toad?

Ric Shine: Absolutely. To somebody that doesn't study toads in excruciating detail you'd have to say that a very high proportion of the toads of the world look incredibly similar.

One of the community groups here in Sydney ran a campaign when we began realised how many cane toads were coming down in building materials and so on, to report cane toads. And I think of the first 100 cane toads reported by the general public 98 were not toads and indeed one was a blue tongue lizard.

People are incredibly bad at identifying frogs in general and cane toads in particular; so it wouldn't surprise me at all if people were to be confused between a black-spined toad and the cane toad.

Zoie Jones: Three other Australian cane toad researchers have seen the photo and agree it's an Asian black-spined toad commonly found in Indonesia. Ric Shine again:

Ric Shine: It's not found in Australia. It's a species that's very widespread in Indonesia and has been expanding its range very rapidly through Indonesia over the last few years.

Zoie Jones: Do you think it's likely that the cane toad has hitched a ride aboard Indonesian forces perhaps into East Timor?

Ric Shine: I certainly think it's incredibly unlikely that it came from Australia. There's been one or two individuals found in ports in Australia over the last few years but it basically doesn't occur here.

I'd imagine there's quite a lot of traffic going on between different parts of Indonesia and East Timor, perhaps including gentlemen in military uniforms.

Mark Colvin: Professor Ric Shine from the University of Sydney ending that report from Zoie Jones.