Indianapolis-based Calumet Specialty Products Partners reported a quarterly net loss of $67.7 million last Thursday as revenue fell 29 percent, from $1.02 billion a year ago to $713 million in this year's first quarter.

Calumet's quarterly loss of $67.7 million compared with a net profit of $23.8 million in the same period of 2015.

"During the first quarter 2016, continued stability in our core specialty products segment was more than offset by a material year-over-year decline in our fuel products segment gross profit, due mainly to weaker refining economics in the regional markets we serve, resulting in a consolidated net loss in the period," Calumet CEO Tim Go said in a written statement.

Lubricating oils sales volume increased to 13,854 barrels per day in the quarter compared to 12,090 barrels per day in the first quarter of 2015.

Calumet, which owns refineries in 10 states across the country, has been hit hard by the collapse in oil prices. Its shares have fallen almost 80 percent since the beginning of the year. The stock fell dramatically last month after the company suspended its annual dividend and took on new debt. It also warned investors that it expected a big loss in the first quarter.

"We are committed to owning and operating a portfolio of assets and product lines that carry sustainable competitive advantages," Go said last Thursday. "We believe every asset in our portfolio must be financially self-reliant to remain part of this long-term portfolio. To that end, we have initiated a comprehensive review of our existing assets that will clearly identify the long-term opportunities, risks and anticipated returns associated with each of our assets, a process which will assist our leadership team in high-grading the portfolio to achieve consistent, profitable growth."

Calumet also said it might divest some of its assets, including a $430 million refinery that opened a year ago in western North Dakota.