ST. PAUL — The state Department of Health says preliminary tests show a white powder found in an envelope opened at the Minnesota governor’s residence was not a biological threat or toxin.

The department has ruled out agents such as ricin or anthrax but will continue monitoring the sample for about 10 days to try to identify it, according to a statement late Monday.

The Minnesota Department of Public Safety said staff at Gov. Mark Dayton’s residence opened the letter Monday morning. While the content of the letter was not threatening, staff detected a small amount of white powder.

The public safety department said Dayton was at the main residence but was “not in close proximity to the letter.”

Reports said no arrests have been made.