The Harvard University Police Department (HUPD) is urging caution after a woman was the victim of an indecent assault in Lamont Library on Friday afternoon.

The woman, who is not affiliated with Harvard University, woke up from a nap around 3 p.m. when she felt something moving beneath her buttocks.

When the victim stood up, she saw a six foot tall, 40-year-old black male with a medium build, medium complexion and short cropped hair. The assailant was wearing a long, black-wool dress coat, a black multi-colored design sweater, and dark pants.

Once seen, the subject grabbed his belongings, including a black backpack, and fled the library.

HUPD detectives and Cambridge police responded immediately to the scene, and stopped a suspect. However, the victim was unable to positively identify him and he was subsequently released.

A similar indecent assault on a female first-year in Annenberg Hall in Sep. led the Freshman Dean's Office to ban tours of Annenberg, but HUPD officers say they are such assaults are the result of the University being in a urban setting.

"The University is an open place and people can sometimes get into parts of it, but [assault] is not a common problem around here," said HUPD Sergeant Kevin P. Bryant.

Advisory e-mails were sent out by HUPD on Friday warning students of the incident.

This was the third such e-mail sent out in two days, following the attempted robbery of a graduate student near Leverett Towers on Wednesday and the hospitalization of a University employee after he drank a contaminated Diet Coke on Thursday.

HUPD urges anyone with information regarding the incident to call the Criminal Investigation Unit at (617)495-1796.