CPL § 410.30 Declaration of delinquency. If at any time during the period of a sentence of probation or of conditional discharge the court has reasonable cause to believe that the defendant has violated a condition of the sentence, it may declare the defendant delinquent and file a written declaration of delinquency. Upon such filing, the court must promptly take reasonable and appropriate action to cause the defendant to appear before it for the purpose of enabling the court to make a final determination with respect to the alleged delinquency.