SB 10.16.4

śrī-śuka uvāca
kālindyāṁ kāliyasyāsīd
 hradaḥ kaścid viṣāgninā
śrapyamāṇa-payā yasmin
 patanty upari-gāḥ khagāḥ
Synonyms: 
śrī-śukaḥ uvāca — Śrī Śukadeva Gosvāmī said; kālindyām — within the river Yamunā; kāliyasya — of the serpent Kāliya; āsīt — there was; hradaḥ — lake; kaścit — a certain; viṣa — of his poison; agninā — by the fire; śrapyamāṇa — being heated and boiled; payāḥ — its water; yasmin — into which; patanti — would fall down; upari-gāḥ — traveling above; khagāḥ — the birds.
Translation: 
Śrī Śukadeva Gosvāmī said: Within the river Kālindī [Yamunā] was a lake inhabited by the serpent Kāliya, whose fiery poison constantly heated and boiled its waters. Indeed, the vapors thus created were so poisonous that birds flying over the contaminated lake would fall down into it.
Purport: 

In this regard the ācāryas explain that the Kāliya lake was situated apart from the main current of the river; otherwise the Yamunā’s waters would have been poisonous even in cities like Mathurā and in other places farther away.