Police are investigating the disappearance of an MIT junior who has been missing for nearly a week.

Daniel S. Mun, commonly known as “Dong,” was last seen around 4:15 a.m. on Dec. 5 as he left his bedroom to use the bathroom at his Chi Phi fraternity house on Hereford Street in Boston, Tom Holtey, treasurer of Chi Phi’s alumni board, said yesterday.

MIT Senior Associate Dean Robert M. Randolph said “there is growing concern” on campus regarding the case.

“We still don’t have an indication of what happened,” Randolph said. “We’ve been searching all of the...places where something might show up.”

A spokesperson from the MIT Police Department declined comment yesterday, referring all inquiries to Randolph.

The MIT Tech, the university’s student newspaper, reported Tuesday that MIT has filed a missing person report with campus police, Massachusetts State Police and the Federal Bureau of Investigation.

Randolph also told the Tech that a boat would be searching the Charles River this week.

Holtey said Mun is a biology major from Missouri and “a very quiet individual.” But he stressed that fraternity members are shocked by the disappearance of Mun, a 5’10 Korean-American weighing about 200 pounds.

Word of Mun’s disappearance made its way to many House open lists yesterday, when one of his friends who is a Harvard undergraduate posted a message asking students here to “be on the lookout and pray hard for his safety.”

“He is a HUGE guy, so it’s not likely that he was kidnapped,” wrote Tatianna C. Bartch ’06. “And as far as anyone knows, he has been happy.”

About a year ago, University of Pennsylvania student David Dantzler-Wolfe disappeared on Dec. 10, 2002.

His body was found in the Schuylkill River this past May.

Ruling that there appeared to be no signs of foul play, an autopsy report could not reveal the cause of death because the body was heavily decomposed, The Daily Pennsylvanian reported last May.

Anyone with information on Mun’s whereabouts can call the MIT Police Department at 617-253-1212 or Randolph at 617-258-5484.

—Staff writer Jenifer L. Steinhardt can be reached at steinhar@fas.harvard.edu.