The two companies agreed last month to move forward with a third year of generative funding for copper exploration in Sonora, with a budget of US$1.3 million.

Riverside said at the time the funding was part of a larger overall package relating to a portfolio of assets the pair had generated over five district areas.

The Canada-based project generator said yesterday BHP had allocated a further $1 million for specific "high value work programmes".

Riverside said the pair had filtered through more than 50 copper districts and the current focus was on five priority BHP-Riverside owned projects.

These were Chuin, Palofierro, Sinoquipe, Penitas and Montosa, in order of priority.

"We are on track with BHP moving toward drill testing and continue progressing a strong pipeline of copper properties that have giant scale exploration discovery potential," Riverside president and CEO John-Mark Staude said.

"As properties move along, some will no longer fit for BHP and these become 100% Riverside so over time Riverside's sole ownership portfolio will also be growing.

"We are pleased to build upon our knowledge in the region and get our teams into the field doing primary exploration work and interacting with communities and local surface ranch and mineral title owners."

London-based Hochschild Mining had exited an earn-in option with Riverside on a gold-silver project in Mexico in May.

Riverside shares (TSXV: RRI) are trading near a one-year low, closing up 3% yesterday to 17c, valuing it at $11.6 million (US$ 9.4 million).