New York City prosecutors have dropped a harassment case against a sister of the Boston marathon bombers after saying that allegations that she threatened to "put a bomb on" a perceived romantic rival couldn't be proven.



The Manhattan district attorney's office said Monday it had "significant" questions about the credibility of the woman who accused Ailina Tsarnaeva.



Tsarnaeva's lawyer hasn't immediately returned a call. Authorities haven't publicly identified Tsarnaeva's accuser.



Prosecutors had said Tsarnaeva had threatened a woman by saying she knew "people that can put a bomb where you live."

She previously pleaded guilty to misleading police who were investigating counterfeiting.



The death penalty phase of the federal trial of Tsarnaeva's brother Dzhokhar Tsarnaev is unfolding in Boston. He was convicted last month in the 2013 bombing.



His brother Tamerlan was killed during the subsequent manhunt.