Detectives in Montgomery County are investigating the sexual assault of a 28-year-old woman in Gaithersburg.

According to police, the attack occurred about 9:40 a.m. Wednesday at an apartment complex in the 700 block of Quince Orchard Boulevard.

Police said that a man followed the woman into a laundry room in the apartment building.

Once inside, the man took out a knife and sexually assaulted the woman, then left the laundry room.

Police said the woman did not know the suspect. He is described as a black man, approximately 20 to 25 years old, about 6 feet tall with a thin build, and wearing a dark-colored sweatshirt and blue jeans.

Anyone with information about the assault or the suspect can call 240-773-5070 or 1-866-411-TIPS (8477), or send a text message to 274637 with “MCPD” in the message.