The CEO of embattled Dakota Plains Holdings has resigned to “voluntarily assist with the company’s efforts to reduce expenses,” according to a federal securities filing.

Craig McKenzie, the oil transportation company’s CEO since February 2013, left the post Monday, though he remains a member of its board of directors.

“Mr. McKenzie’s resignation was not the result of any disagreement relating to the company’s operations, policies or practices,” Wayzata-based Dakota Plains said in a filing with the U.S. Securities and Exchange Commission.

Gabriel Claypool, Dakota Plains’ president and chief operating officer, will now also serve as CEO. Claypool, 40, had been Dakota Plains’ CEO from February 2011 to February 2013, when he was replaced by McKenzie, who is in his early 50s. Claypool was also a member of the company’s board from 2011 to May 2015.

McKenzie had a base salary of $425,000 in 2014 and also received a cash bonus of $425,000 in that year, the most recent compensation data available for the company.

Dakota Plains, which loads oil into rail cars in North Dakota, posted a net loss of $25 million in 2015 and a net loss of $5.1 million through the first half of this year. Its stock was trading at 1 cent Tuesday.

Dakota Plains went public in March 2012 and its shares quickly hit $12. By October of that year, though, they had fallen below $5 and dwindled to around $2 by early 2015 before falling off the map. A deadly oil train derailment in Canada, the global decline in oil prices and other factors have consistently hurt the company’s bottom line.

The SEC in December disclosed that it was investigating the initial spike in Dakota Plains’ shares for stock manipulation. The investigation led the SEC this summer to issue a “Wells notice” to Michael Reger, who was then CEO of Wayzata-based Northern Oil and Gas. The notice indicated the SEC was pursuing an enforcement action against Reger — an early investor in Dakota — for possibly violating securities laws.

Reger was terminated by Northern Oil in August after he notified the company he had received the SEC notice. Dakota Plains itself said it isn’t the target of an SEC investigation.