An unidentified intruder entered the bedrooms of sleeping Saybrook students early Thursday, according to Saybrook Dean Paul McKinley.

In an e-mail sent this morning, McKinley alerted Saybrook students to their college’s uninvited guest, who the dean said entered students’ bedrooms at about 3:30 a.m.

“Although he harmed no one and took no property, the master and I are deeply concerned about this incident,” McKinley wrote.

He added that Yale Police are investigating, and said students should make sure to close and lock their suite doors and report any that are broken.

Saybrook had another intruder this past February, when a man was spotted in a suite looking for items to steal. An alert Saybrook student called police, and the thief was arrested in the college’s basement.

UPDATE: 5:05 p.m. In a second e-mail, sent to Saybrook students just before 5 p.m., McKinley said the intruder’s entry “is an isolated incident, most likely involving a Yale student with entryway access, rather than someone from outside Yale.”