Chelsea have warned fans they will take the "strongest possible action" against anyone found guilty of making threats against referee Tom Henning Ovrebo.
Ovrebo was understood to have been smuggled out of the country by police on Thursday, having received a number of death threats after failing to award Chelsea a penalty during their Champions League semi-final against Barcelona.
But a statement from Chelsea read: "Chelsea Football Club would like to make clear that it condemns any form of threat against players, officials or supporters. If provided with proper evidence Chelsea will take the strongest action against any season ticket holders or members who have participated in this activity."
It continued: "Everybody connected with Chelsea is very disappointed with the events of last night.
"However we would stress that we have received no evidence that Chelsea fans are involved in any of the alleged threats reported.
"As a result of these reports we have also been in contact with the police who likewise had not received any complaints."
Ovrebo turned down four penalty appeals - two for handball - and Chelsea crashed out of the competition when Andres Iniesta scored a 93rd-minute away goal.
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