Ann Arbor police say they have received more than 200 tips as they investigate five recent attacks on women in the city, including two rapes a week ago Monday.

In addition, Crime Stoppers received more than a dozen tips since Friday, said Rich Kinsey, the organization's Washtenaw County coordinator, who also is a contributor for AnnArbor.com.

Police spokeswoman Lt. Renee Bush said people have called with descriptions of possible suspects or witnesses. Others have called believing they recognize the man in the sketch released in the first of the two rapes, she said.

"We are continuing our investigation and we still want the community to be the eyes and ears for us," Bush said. "We are taking this very seriously."

The University of Michigan Department of Public Safety has received more than a dozen tips related to the attacks, Spokeswoman Diane Brown said. Those tips are being forwarded to city police.

Brown said the department continues to patrol the edges of campus closely and communicates regularly with city police on the investigation.

Ann Arbor Police released this composite sketch of a man suspected in a rape on South State Street.

Here's a list of attacks:

10:10 p.m. July 15 — A 21-year-old Ann Arbor woman was walking near Thompson and East Liberty streets when a man grabbed her around the neck. She resisted, broke free and was not injured. The attacker was described as white, 29 years of age, 5 feet, 7 inches tall, 165 pounds, with a medium build.

11 p.m. July 15 — A man grabbed a 19-year-old Ypsilanti woman in the 400 block of North Division Street near Community High School and attempted to pull her into a secluded area, but she got away.

2 a.m. July 16 — A man grabbed a 22-year-old Ann Arbor woman from behind in the 900 block of Greenwood Avenue, lifted up her dress and fondled her before she broke free. The man was described as 5 feet, 6 inches tall with an olive complexion. He had no facial hair and was wearing a zipped-up black hooded sweatshirt and khaki cargo pants. It was the same description of the man involved in the North Division Street attack.

12:40 a.m. July 18 — An 18-year-old Ann Arbor woman was pulled into an alley and raped in the 700 block of South State Street near the University of Michigan. The attacker was described as white, between 5 feet, 6 inches and 5 feet, 10 inches tall, with brown hair and brown eyes. He was wearing a green T-shirt and khaki cargo pants.

10:30 p.m. to 11 p.m. July 18 — A man followed a 26-year-old Ypsilanti woman into an elevator in the Liberty Square parking structure and raped her. The attacker was described as white, 26 years of age, 5 feet, 6 inches to 5 feet, 7 inches tall, with short, dark and straight hair, police said.

A poster seeking information leading to the arrest of a sexual assault suspect hangs in an elevator at the Liberty Square parking structure on Tuesday afternoon. Melanie Maxwell I AnnArbor.com

Crime Stoppers is offering up to a $1,000 reward for information leading to an arrest in any of the attacks. All callers will remain anonymous, Kinsey said.

"It's kind of a blanket for all of them," Kinsey said of the reward, "but if there are multiple suspects, there could be multiple rewards."

Anyone with information can call the Ann Arbor Police Department's tip line at (734) 794-6939 or Crime Stoppers at 1 (800) SPEAK UP.

- AnnArbor.com reporter Heidi Fenton contributed to this article

Lee Higgins covers crime and courts for AnnArbor.com. He can be reached by phone at (734) 623-2527 and email at leehiggins@annarbor.com.