Zimbabwe has launched an investigation into the country's former first lady Grace Mugabe, over her alleged involvement in an ivory smuggling ring.

The probe was opened after a three-month undercover mission, by Australian wildlife photographer Adrian Steirn.

Steirn said he uncovered the poaching and smuggling syndicate, when he began looking into the illegal ivory trade in December last year.

Ivory was being sourced either from the national park's vault, being thieved or pilfered, or from live elephants being killed by poaching syndicates.

The syndicate would then sell to Grace Mugabe's clientele.