Kenyan police said on Monday that ivory trade investigator Esmond Bradley-Martin had been found dead in his home by a family member.

The relative had gone to check on Martin at his home in the Nairobi suburb of Langat on Sunday afternoon after he did not respond to phone calls.

Read more: Risky business: On the trail of poachers in Zimbabwe

"He was found dead in his house and had stab wounds," said a police officer. "An investigation has been launched."

The head of the United Nation's Environment Program, Erik Solheim, said he was shocked by Martin's murder and described the late investigator as a "global authority" on ivory and rhino horn trafficking.

Martin, an American citizen who had lived in Kenya for decades, was a key figure in the global crackdown on illegal ivory supply chains. Much of his research quantified and analyzed the Asian ivory markets in China, Hong Kong, Vietnam and elsewhere.

Watch video 01:37 China clamps down on ivory trade

Instrumental in pushing China's ivory ban

A former UN special envoy for rhino conservation, Martin's research was seen as instrumental in pressuring the Chinese government to ban its legal rhino horn trade in 1993 and end legal ivory sales last year, a ban that came into effect on January 1. Hong Kong also introduced its own ban earlier this month.

"He was one of the most important people at the forefront of exposing the ivory trade, addressing the traffickers and dealers themselves," said Paula Kahumbu, chief executive of the Wildlife Direct conservation group. "His work revealed the scale of the problem and made it impossible for the Chinese government to ignore. It's a very big loss for conservation"

Kahumbu also took to Twitter to celebrate Martin and his work, writing that "pachyderms have lost a great champion."

Martin was about to publish a report exposing how Asia's ivory trade had shifted to China's neighboring countries following the ban.

Martin is the second prominent wildlife conservationist to be killed in eastern Africa in recent months. South African Wayne Lotter, whose work also targeted illegal ivory smuggling from Africa to Asia, was shot dead in Tanzania in August.

Some 110,000 elephants have died at the hands of poachers in the past decade, with transnational crime syndicates taking on much of the resulting illegal ivory trade. The most recent figures for 2016 showed that the ivory market continued to thrive despite a record number of ivory seizures and decline in poaching.

dm/msh (AP, Reuters, AFP)