Investigators say they believe they have identified the man who sexually assaulted and robbed a woman earlier this week in a grassy area near 15th and Vine Streets.

The District Attorney's Office issued a warrant Friday for Elvin Tate, 46. He faces robbery, aggravated indecent assault, theft, and other charges.

Tate remained at large Friday, though he has been spotted this week outside Center City bars and restaurants, said Capt. John Darby, commander of the Special Victims Unit.

"He's certainly dangerous," he said. "He choked that woman. He also used a knife."

Darby also said he was concerned because of "the boldness, the craftiness" of the crime.

The 24-year-old victim went out looking for her roommate early Tuesday. She was concerned because the roommate had not come home, Darby said.

Tate convinced the victim that he had seen her roommate and that he could help find her friend, Darby said.

At 15th and Vine, he assaulted the woman, took her debit card, and made her divulge her PIN. By the time the woman reported the assault around 3 a.m., Tate had made withdrawals from her bank account.

A surveillance camera at an ATM he visited at 18th and Market Streets captured a high-quality picture of Tate, and Darby said he had been identified through tips and "aggressive investigation."

Tate has several former addresses in Philadelphia and outside the city. Detectives visited his last known address in South Philadelphia, but he no longer lived there, Darby said.

Tate told his victim that he was homeless, and he is known to frequent the area around John F. Kennedy Plaza, where the homeless often congregate.

But Darby said the victim did not believe he was homeless.

"I wouldn't put that label on him, nor would the victim," he said.

Darby said Tate had lived in the Scranton and Harrisburg areas and had been arrested there. Court records in Philadelphia showed one minor alcohol-related arrest.

Darby said Tate has no record of sex crimes.

He is listed as 6-foot-3 and 280 pounds.

Anyone with information is being asked to call the Special Victims Unit at 215-685-3251.

Contact staff writer Troy Graham at 215-854-2730 or tgraham@phillynews.com.