BRUNSWICK, Maine — About 20 Bowdoin College students launched a sit-in Wednesday morning outside President Barry Mills’ office, refusing to leave until the administration commits to working with them to eliminate all fossil fuel investments from Bowdoin’s $1.2 billion endowment.

Members of Bowdoin Climate Action sat with laptops and backpacks on chairs and along the floor of the hall outside Mills’ office just after 10 a.m. Wednesday, quietly reading or writing. Mills’ door remained closed and students said they did not know if he was present.

“We want them to collaborate with us,” said Bowdoin senior Matthew Miles Goodrich, 21, of Brookfield, Connecticut. “We proposed divestment to the the president of the board of trustees in October and we’ve been ignored by them for about 150 days. This is the college for the common good. Fossil fuel is a threat not only to the students in this room but to … millions of people across the globe [and] more often than not, people from marginal countries.”

“We’re not going to leave until we make our point,” Goodrich said, clarifying that “that depends on when the administration engages — and we’ll make sure they do. We’re really prepared for everything.”

Student Julianna Lewis sent an email to Mills, Dean of Students Tim Foster and Mills’ executive assistant, Rebecca Smith, just after 9 a.m. Wednesday, alerting them to the protesters’ presence and urging college officials to issue a formal public statement that they will pursue divestment in collaboration with the Bowdoin community.

In an email reply to Lewis, Mills wrote, “Dear Julianna, Thank you for your message. Regards, Barry.”

College spokesman Doug Cook said later Wednesday morning that Mills is traveling on college business. Cook was not sure when Mills was expected to return.

Mills has met with students on numerous occasions about divestment but has no plans to change his opposition to the proposal, Cook said Wednesday.

“President Mills has made his position and that of the college pretty clear,” Cook said. “That’s not changing … While he shares their deep concerns about climate change, he has explained his opposition to the largely symbolic action of divestment, and thinks the college should focus its efforts on education and effective action to confront what is a very real negative consequence of climate change.”

Bowdoin’s endowment generated an investment return of 19.2 percent in fiscal year 2014, The Orient, the college’s student newspaper, reported, bringing its market value to $1.216 as of June 30, 2014. As a result of the gain, the college earned “Endowment of the Year” from global finance magazine Institutional Investor, according to The Orient.

Cook said he was not sure how much of the college’s endowment is currently invested in fossil fuels, but in February 2013, Mills and Paula Volent, senior vice president for investments, told The Orient that approximately 1.4 percent of Bowdoin’s endowment is invested in 200 publicly traded fossil fuel companies companies. The college invests in them through large commingled funds that contain hundreds of other stocks. Divesting from fossil fuels would require a turnover of more than 25 percent of the endowment, they told the college newspaper.

Students presented their divestment proposal to trustees in October, the Orient reported, and at a February rally called for a trustee liaison by March. According to Goodrich, Mills appointed himself as that liaison — which Goodrich said “is absurd because he’s leaving in July.”

Mills will retire from Bowdoin this summer. Clayton Rose has been appointed the college’s next president.

Cook said the students would not face disciplinary action as a result of the sit-in “as long as they’re not impeding the business of the college.” He said administrators have no plans to remove the protesters from Mills’ office when the office closes Wednesday evening.

He also referred to previous editorials and columns in The Bowdoin Orient, noting, “There are many students who do not feel this way.”