The Police Department could not save 7-year-old Nixzmary Brown because child welfare officials did not inform detectives about reports of alleged abuse, the Police Commissioner, Raymond Kelly, testified before the City Council’s general welfare and public safety committees yesterday.

Indeed, when detectives responded on December 1 to a report of physical abuse from a social worker at the Brooklyn girl’s school, child welfare workers assured detectives that “everything was all right” and the detectives did not need to be present, Mr. Kelly said.

Nixzmary died on January 11 from child abuse syndrome, including blunt impact injury to the head. Her body was covered in bruises, she was malnourished, and she had missed 46 days of school, officials said. Her mother, Nixzaliz Santiago, 27, and stepfather, Cesar Rodriguez, 28, were charged with her murder on January 17 by the district attorney’s office last month. Mr. Kelly said the Administration for Children’s Services “didn’t think it was necessary to provide this information” to the police.

The City Council questioned whether Nixzmary’s case should have been categorized as the most severe, requiring an instant coordinated response from ACS and law enforcement.

If it had been, Mr. Kelly said, “a whole different procedure would have been put in place.”

Speaking at an unrelated event yesterday morning, Mayor Bloomberg said, “The trick is to make sure” that “the right people are called and the right information is given clearly, and timely, and an in appropriate manner.”

Of the approximately 50,000 calls of alleged abuse and/or neglect that children’s services handled in 2005, 2,806 required an instant response team, Ms. Stainback said.

In the six weeks since Nixzmary’s death, the number of reports of child abuse has more than doubled. Between January 12 and February 10, there were 572 cases citywide that required an instant response team, according to an ACS spokeswoman, Sheila Stainback. For the same period last year, there were 261.

The surge in child abuse reports has added to the caseloads of investigators from the police department’s Special Victims Unit, assigned child abuse and all serious sexual offense cases, Mr. Kelly said.

“Over the past month, our Special Victims Division caseload has jumped almost 65%, with a 226% increase in instant responses,” Mr. Kelly said. “If this trend continues, the average caseload of a Special Victims detective will increase from 48 cases to 93 cases” by the end of the year. The Police Department is conducting a review of its protocol in response to reports of abuse, and plans to present its findings to Mayor Bloomberg on March 10, Mr. Kelly said.