Matsya Purana 249.69

249.69

babhūvātra mahāghoṣo mahāmegharavopamaḥ.
udadhermathyamānasya mandareṇa surāsuraiḥ .. 249.69 ..

Now here, then, was a thundering din caused by the churning of the ocean, thousands of the aquatic beings fell dead by the blow of the Mandara mountain.—69 70