ST. PAUL — A Minnesota Pollution Control Agency staff member involved in the environmental review of the Sandpiper crude oil pipeline won’t be disciplined for emails containing a critical tone about the project, the agency’s head said.

In a letter dated Saturday, MPCA Commissioner John Linc Stine said a state investigation “did not produce any cause for disciplinary action.”

The investigation began after the Pioneer Press reported in January on 2014 emails from MPCA environmental specialist Scott Lucas to activists fighting Calgary, Alberta-based Enbridge’s proposed 616-mile pipeline that would bring North Dakota oil across northern Minnesota to Wisconsin.