MINNEAPOLIS — A Minnesota prosecutor said Tuesday that he would agree to review allegations of domestic abuse against U.S. Rep. Keith Ellison only if a formal complaint is first investigated by law enforcement.

An ex-girlfriend of Ellison, Karen Monahan, alleged in August that the Democratic congressman dragged her off a bed by her feet and screamed obscenities at her in 2016. On Monday, a draft report by an attorney with links to the state’s Democratic party found that Monahan’s claims were unsubstantiated because Monahan refused to provide video she said she had of the incident.

Ellison, a deputy chairman of the Democratic National Committee, has denied the allegation.

In a letter dated Tuesday, Dakota County Attorney James Backstrom said the Minneapolis city attorney asked him to provide a preliminary review of the matter, citing a conflict of interest because Ellison’s son is on the Minneapolis City Council.

Backstrom told City Attorney Susan Segal that prosecutors generally do not conduct criminal investigations. He said if Monahan, the state’s Democratic-Farmer-Labor Party, or others want to file a complaint alleging criminal conduct, that must be done with law enforcement. Then, it would be up to police to determine how and when to investigate.