USviewer: Officers summoned to the house at about 3:30 p.m. (1930 GMT) on Saturday found all six stabbing victims on the second floor, one of them already deceased, Anthony Ambrose, Newark's director of public safety, told an evening press conference.
Two of the victims later died of their wounds while the remaining three were hospitalized, authorities said.
The deceased were identified only as an 8-year-old girl, an 11-year-old boy and a 23-year-old woman.
The wounded victims were described as a 29-year-old woman and two 13-year-old children, a boy and a girl.
The woman, the mother of at least one of the younger victims, was listed in stable condition, while there was no information immediately available on the status of the children.
"It is difficult for me to even speak about this, having young children of my own," Newark Mayor Ras Baraka told the news conference. "It kind of makes my stomach churn to imagine the kind of horrific scene that took place early this evening."
No arrests had been made for the stabbings as of Saturday evening.
Authorities said they were seeking to question 26-year-old Jeremy Arrington, who they said was the subject of unrelated warrants for sexual assault and aggravated assault and acquainted with at least one person who lived at the home.
Police and prosecutors said Arrington, a Newark resident, was not a suspect in the stabbings but was considered a "person of interest" and cautioned members of the public to be careful in approaching him.
Essex County Prosecutor Carolyn Murray said that all six of the victims had been stabbed with at least one knife but that "we are not ruling out other weapons at this time" in the attack.
The incident comes one day after two people were stabbed and their suspected attacker injured at Rutgers University's business school in the state. There was no indication that the two incidents were related.