Starting today, some first-years will need a key to use their bathrooms.

Crews from Facilities Maintenance Operations will spend the day installing locks on bathroom doors accessible from common hallways, the Freshman Dean's Office announced Friday.

The new security measures come in response to an incident nearly two weeks ago in which a Hollis Hall resident found a homeless man in her shower.

The man, a 21-year-old from New York, was accosted but was let go last week by officers from the Harvard University Police Department, officials said.

The dormitories affected include Greenough, Hollis, Stoughton, Thayer and Weld, and the first floor of Canaday, according to a note distributed to the affected students.

The Assistant Deans of Freshmen who signed the letter, David B. Fithian, D.E. Lorraine Sterritt and Eleanor A. Sparagana, were not available for comment this weekend.

Merle A. Bicknell, manager of Harvard Yard facilities, said the new security measures underlie a more important security concern.

"We're trying to get the word out to the freshmen that they really should treat their dorm as their home," she said.

Specifically, she said, she wants all students to ask to see the identification of all who seek entry to a first-year dorm.

Bicknell said that after the Hollis shower incident, she "dressed in casual clothes" and tried to access all the first-year dorms without identification or a card key.

"I was able to walk in without being questioned every time," she said.

Questioning strangers, then, "is the message we need to get out," she said.

Some students said they will not mind the bathroom locks.

"It's not a serious inconvenience, since we lock our doors and we're supposed to carry our keys with us anyway," said Thayer resident Steven P. Schwartzberg '01.

But another Thayer resident disagreed.