Chelsea have launched an investigation after a smoke bomb was detonated at the club's training ground in the latest offbeat incident at the complex, it was reported on Saturday.
The Daily Mail reporters players and officials were forced to evacuate the training ground building on Friday after the smoke grenade was let off.
"I can confirm an investigation is under way. It is an internal matter," a Chelsea spokesman said.
Last year Blues defender Ashley Cole made headlines after accidentally shooting a work experience student with an air rifle at the ground while later in the year a hunting knife was found in a dressing room.