Mbh 9.43.1a

Vaishampayana said, "Cursed by the intelligent Vishvamitra in anger, Sarasvati, in that auspicious and best of tirthas, flowed, bearing blood in her current. Then, O king, many Rakshasas came, O Bharata, and lived happily there, drinking the blood that flowed. Exceedingly gratified with that blood, cheerfully and without anxiety of any kind, they danced and laughed there like persons that have (by merit) attained to heaven. After some time had passed away, some Rishis, possessed of wealth of asceticism, came to the Sarasvati, O king, on a sojourn to her tirthas. Those foremost of Munis, having bathed in all the tirthas and obtained great happiness, became desirous of acquiring more merit. Those learned persons at last came, O king, to that tirtha where the Sarasvati ran a bloody current. Those highly blessed ones, arriving at that frightful tirtha, saw the water of the Sarasvati mixed with blood and that innumerable Rakshasas, O monarch, were drinking it. Beholding those Rakshasas, O king, those ascetics of rigid vows made great endeavours for rescuing the Sarasvati from that plight. Those blessed ones of high vows, arrived there, invoked that foremost of rivers and said these words unto her, 'Tell us the reason, O auspicious lady, why this lake in thee hath been afflicted with such distress. Hearing it, we shall endeavour (to restore it to its proper condition).' Thus questioned, Sarasvati, trembling as she spoke, informed them of everything that had occurred. Seeing her afflicted with woe, those ascetics said, 'We have heard the reason. We have heard of thy curse, O sinless lady! All of us shall exert ourselves!' Having said these words unto that foremost of rivers, they then consulted with one another thus, 'All of us shall emancipate Sarasvati from her curse.