The mystery surrounding the deaths of at least 877 dolphins in Peru deepened on Wednesday as the government said human activity was not to blame but failed to pinpoint a natural cause for the massive die-off.

A final report from the Peruvian government's Ocean Institute, which manages one of the world's richest marine ecosystems, said the dolphins did not die from a lack of food, hunting by fishermen, poison from pesticides, heavy metal contamination, an infection or a virus.

A Peruvian minister has denied claims that explosions used in oil exploration are to blame for the deaths of hundreds of dolphins.

Fisheries Minister Gladys Triveno said a government investigation showed that natural causes were to blame.

She contradicted a study by an environmental group which suggested that explosions had caused the deaths.

The animals have washed up along Peru's northern coastline since the beginning of the year.

A microfinance provider in Karnataka has been selected alongside seven other organisations from Peru, Indonesia, Cambodia and Afghanistan as a finalist for the Ashden Awards, the world’s leading green energy prize.

The finalists will compete for over £120,000 pound prize, with the winners to be announced at a prestigious ceremony in London on May 30. Shri Kshethra Dharmasthala Rural Development Project in Karnataka is a prime example of the vital role a well-run microfinance organisation can play in meeting the poor’s energy needs.

While its Latin American neighbors move forward with national climate laws, Argentina is backsliding on actions to tackle its greenhouse gas emissions as the country struggles to meet energy demand from a fast-growing middle class.

Argentina's GDP grew 7.3 percent last year, driving demand for energy that is overwhelmingly derived from fossil fuels. According to Argentine Institute of Petroleum and Gas (IAPG), energy demand rose 5.1 percent in 2011.

Late last year, fishermen began finding dead dolphins, hundreds of them, washed up on Peru’s northern coast. Now, seabirds have begun dying, too, and the government has yet to conclusively pinpoint a cause.

Officials insist that the two die-offs are unrelated. The dolphins are succumbing to a virus, they suggest, and the seabirds are dying of starvation because anchovies are in short supply.

Peru became the latest developing country to enact a domestic climate change initiative in the absence of a binding global pact, adopting a resolution on Thursday to lower carbon emissions in its fast-growing economy.

As one of the world's most geographically diverse places, Peru said it is already feeling the effects of a changing climate, such as melting tropical glaciers in the Andes and high levels of solar radiation.

Newmont Mining has shown its "willingness" to improve the environmental mitigation plan for its proposed gold mine known as Conga, Peru's government said on Monday, as it seeks to overcome opposition to the mine.

Mines and Energy Minister Jorge Merino said he would confer with officials from U.S.-based Newmont to define how the mitigation plan would be altered after a team of independent environmental auditors recommended a series of changes that could increase the cost of the controversial project, now estimated at $4.8 billion.

Peruvian President Ollanta Humala said on Friday that U.S.-based Newmont Mining should carry out a more ambitious environmental mitigation plan if it hopes to build its $4.8 billion Conga gold mine project.

Humala, who urged community activists to stop protesting against the stalled mine's construction, said the government would make sure the company adheres to strict social, environmental and labor goals.