Cops were on a sweeping manhunt Friday for a man suspected of raping five women and girls — and who may have struck again.

On Friday night, police surrounded a Denver residence where a woman was assaulted. It was not clear that the attack was sexual, but it did occur in the same area where Brent J. Brents (search) is suspected of committing his crimes, according to Denver police spokeswoman Teresa Garcia.

Police say the suspect may have fled in a 2004 gray Mazda with Colorado license plates. The license plate number is 980KLS. A woman with brown hair was seen in the car.

Brents had confessed to molesting a boy nearly three months ago but slipped through the hands of officers in a Denver suburb.

He is also suspected of sexually assaulting two women at knifepoint in the afternoon Feb. 11, when a 29-year-old woman was attacked in her home in an upscale neighborhood just east of downtown Denver. Three hours later, a 44-year-old woman was sexually assaulted in her business in a nearby, eclectic area.

Police also believe Brents was the knife-wielding man who burst into a house three days later in neighboring Cheesman Park (search), one of Denver's oldest and most exclusive enclaves, and attacked two 11-year-old sisters and their 67-year-old grandmother. A 6-year-old girl who was asleep in another room was unharmed, according to a federal arrest warrant filed Friday in U.S. District Court.

"I think he has the potential for violence. He is a repeat sex offender and pedophile who doesn't differentiate between men and women, boys and girls," Police Chief Gerry Whitman told The Associated Press.

Whitman said Brents was linked by DNA evidence (search) to the string of rapes in Denver. He is also a suspect in the sexual assault of a woman in October. Police also learned that he was wanted by authorities in neighboring Aurora on charges of inappropriately touching his former girlfriend's 8-year-old son.

Aurora police interviewed Brents about the allegations on Nov. 23 and he told officers the boy was telling the truth. An arrest warrant wasn't issued until more than two months later on Jan. 26.

Aurora Police Chief Ricky Bennett has defended his department's actions, saying Brents was allowed to leave after his confession because additional investigation was needed.

"Our goal, again, is to achieve a successful prosecution here, not to make a quick and hasty arrest," Bennett said during a news conference Friday.

Karen Steinhauser, who prosecuted Brents in 1988, said if Brents confessed to molesting the boy, there was probable cause to arrest him in January.

"I would be concerned that you would be putting other people in the community at risk, particularly children," she said.

Now, about 200 officers, working with the FBI and police departments throughout Colorado's metro areas, are checking out up to 400 tips, some from out-of-state.

With tens of thousand of people expected in Denver this weekend for the NBA All-Star game, Whitman said the manhunt is not expected to affect parking or traffic enforcement, which are the major concerns for city officials.

Police don't know if Brents is still in the Denver area or long gone. Whitman said his department has received leads from several other states. Police agencies along Colorado's Front Range are checking out tips they've received.

Whitman said Brents has used the aliases of Michael James Curtis and Michael James. He is described as 5 feet, 8 inches to 5 feet, 10 inches tall, 170 to 180 pounds with brown hair and tattoos.

A $40,000 reward is being offered for information leading to his arrest.

Brents was released from prison last July after being sent to the state hospital for about three years and then sent to prison for 14 years in the rapes of a young boy and girl in separate incidents. Steinhauser said she put together the 1988 deal in which Brents pleaded innocent by reason of insanity to one of the rapes so he could get treatment.

"The whole intention was to get him off the street for a very lengthy period of time. And during that period of time, the intention was also to get him help," said Steinhauser, now a professor at the University of Denver Law School.

When Brents was sentenced, there was no mandatory parole or lifetime supervision for convicted rapists. He couldn't have been sent to prison for life, as he could now.

The Associated Press contributed to this report.