CBC News has learned two federal agencies want a more thorough review of the environmental impacts of chromium mining in the Ring of Fire.

Documents obtained by CBC News under access to information show the Canadian Environmental Assessment Agency (CEAA) was seeking advice earlier this year from other government departments.

It wanted to know how much scrutiny it should give the proposed Cliffs chromite project, 540 kilometres north of Thunder Bay.

In a June 2011 letter, the Canadian Wildlife Service said the agency should "err on the side of caution due to the many uncertainties" associated with the project "and the potential for impacts to migratory birds, species at risk and wetlands."

Madeline Head, who is with the environmental stewardship branch of the Canadian Wildlife Service, recommended the CEAA put the Cliffs project to "a higher level of assessment and scrutiny ensuring rigorous assessment of the project effects ..."

Not enough baseline information

An Ontario manager with Environment Canada raised several concerns about the Cliffs project in his letter to CEAA last fall.

Rob Dobos said there isn't enough baseline information about hexavalent chromium (a potentially deadly by-product of chromium mining) to determine whether there will be adverse effects on water quality and wildlife.

He also said, if Cliffs decides to build its smelter on or near First Nations lands "the lack of applicable federal regulatory controls for these emissions would also be a concern."

Dobos recommended a regional environmental assessment process "that considers the interconnectivity and the cumulative impact of currently proposed and anticipated future developments within and connecting to the Ring of Fire."

He said another proposed project in the Ring of Fire by Noront Resources should be included in the regional assessment.

But the CEAA has so far ignored the advice, as it continues with a paper-based comprehensive study of the Cliffs project launched in the fall.

Meanwhile, Noront Resources will hold a public open house in Thunder Bay on Thursday for people to learn more about its mining plans.