Police released this sketch of a man suspected of being a possible serial rapist. (LAPD)

Authorities say a possible serial rapist may be stalking women on skid row after what appears to be a second sexual assault involving a van driver in as many weeks.

The suspect is believed to be a middle-age man who drives a Ford Econoline-style van.

The first attack occurred Aug. 1 when a 37-year-old transient woman accepted a ride near 6th Street and Stanford Avenue in skid row. The victim told detectives that the assailant bound her with duct tape and raped her repeatedly over the next three days. The suspect eventually released her in Koreatown.

"The challenge for us in this case was the victim's apprehension to cooperate," said Los Angeles Police Lt. Paul Vernon, who heads the Central Detective Division. "It was difficult for officers to get any useful information from her, and since that night we've been unable to locate her."

On Monday about 10 p.m., two women were walking near 6th Street and Towne Avenue, not far from where the first victim was picked up. They were approached by a middle-age, balding man in a brown van. He offered a ride to get food. Vernon said one of the women accepted and they drove to a McDonald's restaurant at 7th and Alameda streets.

There, the man told the woman he wanted her to perform a sex act, Vernon said. When she refused, the assailant pulled a knife and used duct tape to bind her arms and legs and gag her, Vernon said. The man drove to an industrial area of Alhambra and raped her, Vernon said.

The suspect then threw the victim, still naked, bound and gagged, into a trash bin and drove away. A nearby business owner discovered her, Vernon said.

"These types of stranger rapes and abductions are quite the exception, and we take them very seriously," Vernon said.

LAPD officers and detectives continue to patrol skid row for the van, he said. Detectives plan to release a composite sketch and possibly video footage in the coming days.

According to Vernon, the last series of sexual assaults in skid row occurred in 2008. Eric Lamont Clay, 37, was arrested and charged in the rapes of at least four women, whom he picked up in his taxi.

Police are asking anyone with information to call Det. Josh Riggs, Central Division sex crimes unit, at (213) 972-1235.