A government investigation of a leading Arctic scientist has moved on from his five-year-old paper on drowning polar bears to a current study on how the animals are coping with changing ice conditions.

Charles Monnett, who was suspended on 18 July from his job as a government wildlife biologist, received an official letter on Monday indicating he would face questioning on his oversight of research contracts.

Until his suspension, Monnett oversaw $50m (£30.6m) in research contracts – among them a study conducted by scientists from the University of Alberta on how polar bears were responding to their changing habitat.

That study now appears to be the focus of the investigation.

"We intend to discuss actions taken in your official capacity as a biologist and any collateral duties involving contracts as an official of the US government," Eric May, an official in the department of interior's inspector general's office wrote in the letter.

"Those actions include the procurement of a sole source, cost-reimbursable contract with the University of Alberta to conduct a study titled 'Populations and Sources of the Recruitment in Polar Bears.'"

The letter asked Monnett to meet government investigators on 9 August. Public Employees for Environmental Responsibility (Peer), which is acting as Monnett's defence team, said Monnett will be asked about his compliance with government contracting regulations as well as his relationship with the lead researcher, a reputed polar bear scientist, Andrew Derocher.

Jeff Ruch, the president of Peer, said Monnett's management of the polar bear study had been approved by his supervisors at the Bureau of Ocean Energy Management Regulation and Enforcement (BOEMRE).

"Every aspect of this study was approved by his chain of command, with a fairly transparent paper trail," Ruch said in a statement.

Ruch noted that the justice department had turned down the investigators' request to file criminal charges against Monnett. The government ordered scientists to halt work on the study on 13 July.

According to documents obtained by the Guardian, the study, conducted by scientists from the University of Alberta, was using satellite collars to track polar bears and their response to changing ice conditions. About 20 bears are still wearing the collars.

The letter to Monnett from the interior department's inspector general marked the first time the scientist has been informed of the scope of an investigation that has already been under way for months.

Peer initially suggested that the government was homing in on Monnett's 2006 paper, which first exposed the threat to polar bear from the melting sea ice due to climate change.

Ruch also suggested at the time that the government was trying to sideline Arctic research to help open up the region for offshore oil drilling.

"You have to wonder: this is the guy in charge of all the science in the Arctic and he is being suspended just now as an arm of the interior department is getting ready to make its decision on offshore drilling in the Arctic seas," Ruch said.

Two interviews conducted by the investigators, with Monnett and a colleague, Jeff Gleason, focused heavily on that 2006 research paper, which exposed the threat of drowning to polar bears.

Monnett's observations, which were published in 2006, marked the first time scientists had drawn a connection between melting sea ice produced by climate change and the increased risk of drowning to polar bears.

Other studies have confirmed Monnett's findings. A study last month from the World Wildlife Fund found that polar bear cubs forced to make long-distance swims with their mothers had a much poorer rate of survival than bears that didn't have to swim as far.

But Michael Bromwich, the head of BOEMRE, insisted the paper had nothing to do with the investigation. The controversy over Monnett has been an embarrassment for the agency, which was renamed after last year's BP oil spill disaster exposed the overly close relationship between government regulators and the industry they were meant to be regulating.

In particular, the agency's Alaska office was criticised for failing to offer rigorous environmental assessments of the potential impact of offshore drilling in a report by the Government Accountability Office last year.