Philadelphia police continued their search yesterday for clues in the sexual assault of two women Friday in their apartment in the 4400 block of Spruce Street.

Police at the University of Pennsylvania, where the victims were students, also stepped up patrols over the weekend in response to the attacks.

A Philadelphia police spokesperson said the department did not know how the attacker entered the apartment building. Once inside, he approached one of the women in the hallway about 3 p.m. and used a knife to force her back into her apartment.

The assailant is described as a black man in his mid- to late 20s, standing between 6 feet and 6 feet, 2 inches tall, and wearing a goatee.

He bound and gagged the 22-year-old woman and robbed her of a laptop, cell phone, iPod and cash. About 4:15 p.m., the victim's 24-year-old roommate arrived at the apartment. She was bound and gagged, sexually assaulted, and robbed of an iPod, cash, bank card and cell phone, police said.

The assailant wore a mask and cotton gloves and made the victims shower after the attacks, apparently to eliminate evidence, police said.

Penn president Amy Gutmann said the women had been treated at a hospital and had returned home to their families.

Police said the attacker resembled a man who forced a woman and her boyfriend into her apartment in the 900 block of Clinton Street on Oct. 22, bound and gagged them, then raped the woman and robbed them.

Some people in the area yesterday had not heard of the attacks, but resident April Coleman said the news made her angry. "It makes you wonder - why do people do these things?" she said.