Robert Pattinson, Kristen Stewart, Taylor Lautner and New Moon filmmaker Chris Weitz cleared the premises in central London, following a fire alarm going off during press interviews for the forthcoming sequel, E! reports.
Eyewitnesses on the scene said that "everyone was out on the street" after the event, which transpired around lunchtime.
"There [Rob] was with his entourage, including Kristen," another source added.
A spokesperson for The Dorchester Hotel called the mass departure a "minor incident", adding: "It's all under control now and was dealt with quickly".
New Moon arrives in cinemas on November 20.