PORTLAND – The gender lines are being blurred in some dorm rooms at the University of Southern Maine.

USM is one of about 20 colleges in North America, and the only one in Maine, that allows men and women to live in the same room.

USM launched its gender-neutral housing program in 2004 to offer gay, lesbian and transgender students an alternative housing arrangement on campus.

Now a growing number of students who simply are comfortable living with a friend of the opposite sex, regardless of sexual orientation, are signing up, school officials say.

About 50 men and women take part in the program, which represents about 3 percent of the school’s 1,454 dorm beds, according to the Residential Life Department. The gender-neutral rooms are located in Portland Hall in Portland and Philippi Hall on USM’s Gorham campus.

Micah and Hannah Blizzard, a brother and sister from Conway, N.H., live together in a room in Portland Hall. The Blizzards attend Southern Maine Community College, whose students share the dorm with those from USM and the Maine College of Art.

Micah Blizzard said students make a lot of transitions in college, and deciding whom to live with can be one of the most difficult. The Blizzards ended up living together because they applied late for housing, but neither flinched when the opportunity presented itself.

Coed suites – where men and women have different bedrooms but live within the same suite – are offered at Maine’s other public and privates colleges and universities, but USM is the only one where men and women may share the same room.

In December, Clark University in Worcester, Mass., changed its student housing policy to allow coed living.

Next fall, students at Clark will have a gender-neutral housing option. Jeffrey Chang, a sophomore, said he simply wants to share a room with a female friend he is comfortable with and who has a similar background and interests.

“Finding a good roommate is difficult enough, and if you find someone who is the opposite sex, it shouldn’t matter,” he said.

Denise Nelson, USM’s director of residential life, said students are not questioned when applying to the program about why they want to live together, but they are asked to talk to their parents about it beforehand.

Nelson said the program mirrors off-campus housing, where men and women are able to live together without question as long as they pay rent.