JOHANNESBURG (AP) — A new study says the illegal sale of ivory in open markets in Central Africa has been disappearing or going underground. But it warns that corruption and weak governance are undermining efforts to curb regional trafficking.

Wildlife trade monitoring group TRAFFIC says in an analysis released Thursday that while law enforcement operations put pressure on open ivory markets, criminal syndicates are exploiting "official collusion, confusion and corruption" to benefit from elephant poaching.

The survey was conducted over the last decade, most recently in 2015. TRAFFIC investigators visited cities across Cameroon, Central African Republic, Congo, Republic of Congo and Gabon.

China, the world's largest ivory consumer, says it plans to shut down its ivory trade by the end of this year in an effort to curb the slaughter of African elephants.