A Brooklyn woman accused of drowning her three children in the waters off of Coney Island last month was indicted on murder charges on Thursday, prosecutors said.

Erin Merdy, 30, of Coney Island, was charged with three counts of first-degree murder and nine counts of second-degree murder during her appearance in Brooklyn Supreme Court, the Brooklyn District Attorney’s office said in a press release. 

At her initial arraignment, she was charged with seven counts of murder, including murder in the first degree, the DA’s office previously said. 

“These innocent young children had their entire lives ahead of them when their own mother allegedly drowned and left them on a Coney Island beach,” Brooklyn District Attorney Eric Gonzalez said in a statement. “This is a shocking and unspeakable crime, and with this prosecution, we will seek justice.” 

Merdy underwent psychiatric evaluation at NYU Langone Hospital in Brooklyn after she was arrested. According to Department of Correction records, she is currently being housed at the Rose M. Singer Center on Rikers Island.

Prosecutors said Merdy drowned her three children — 7-year-old Zachary Merdy, 4-year-old Liliana Stephens Merdy and 3-month-old Oliver Bondarev — in the ocean off of Coney Island beach, near West 35th Street, around 12:40 a.m. on Sept. 12. 

After Merdy left the children on the beach, she walked toward an apartment that belonged to Bondarev’s father, calling family members in distress as she made her way there, prosecutors said. 

When Merdy refused to say where her children were, Bondarev’s father and her relatives called 911 and began searching for her, according to prosecutors. 

Police officers found the children on the beach’s shoreline around 4:30 a.m., the DA’s office said. They were pronounced dead at NYC Health + Hospitals/Coney Island, the NYPD said. 

Family members found Merdy “wet and barefoot” in Brighton Beach, where she told them her children were “gone” and apologized to them, prosecutors said. 

Merdy faces a life sentence without parole if she is convicted, the DA’s office said. She is expected to appear in court again on Nov. 30. 

Her attorney didn’t immediately respond to request for comment on Thursday.