The gaffe became clear as Riley drew a slightly bent line up Michigan Ave., which was connected to what resembled testicles.
Riley appeared not to notice.
WJRT news director Jayne Hodak told TVSpy that Riley made an innocent error.
“In no way was it intentional,” she said.
Since the 11 p.m. newscast aired Tuesday, the story has gone viral on the web, with dozens of news outlets carrying the story.
Saginaw is about 210 km north of Detroit.