DENVER -- A 28-year-old man charged in connection with the sexual assault of a 13-year-old girl has investigators concerned there may be other victims.

Chad Yancey, 25, who was a guest of the victim's family, is accused of attacking the teen as she did laundry in the basement of her home, Denver district attorney spokeswoman Lynn Kimbrough said Wednesday.

The charges also allege that Yancey then threatened the victim’s brother with a knife as he chased Yancey out of the house and down the street, where Denver police officers confronted and arrested him, Kimbrough added.

Yancey was formally charged last month with sexual assault, kidnapping and menacing, she said.

Investigators believe there could be additional victims and are asking anyone with information to call Investigator Jeff Watts at 720-913-9168.