Two more poisoned pigeons plummeted to earth in San Francisco yesterday, and investigators continued searching for the culprit responsible for sprinkling tainted birdseed. 

The dead birds, found in the Castro District and at Treat and Florida streets, were believed to have been killed by ingesting the same strychnine-laced birdseed that killed 35 birds earlier in the week. 

Dispatchers at the Department of Animal Care and Control have received about 50 calls with possible leads, but no suspects have been identified. 

On Tuesday, investigators found the deadly birdseed sprinkled on the ground in a vacant lot at Treat and Florida streets and also inside the bodies of the dead birds. Fourteen of the birds were found in and around Union Square early Monday.