After a tussle over a ball, a 9-year-old Brooklyn girl allegedly stabbed her 11-year-old friend to death yesterday afternoon with a single thrust of a steak knife, police said.

About 1:30 p.m., on the seventh floor of the Linden Houses public-housing complex in the East New York section, police responded to 911 calls from neighbors who saw the body of the 11-year-old, Queen Washington, sprawled in a pool of her blood in the hallway.

The girl was barefoot, wearing red and purple shorts, the caller reported.

“Hurry. Please hurry,” the caller said, according to police. “She was stabbed.”

When detectives arrived at the apartment building shortly afterward, they found that the steak knife lodged in the girl’s chest had pierced her heart – a fatal wound.

“She was just about to graduate from elementary school,” one of the girl’s aunts, Genell Durdin, said.

Another aunt, Sharon Washington, said her niece, who lived at 666 Willoughby St. in Bed-Stuy, had been spending the weekend at the Linden houses with family. She described the slain girl as highly active.

“She liked to rollerblade, she liked to dance,” Sharon Washington said.

Outside the housing complex, a grandmother, who did not identity herself, sought donations for a funeral.

During the stabbing, the 9-year-old’s mother – who is also godmother to the slain girl – told police she had left their apartment on the seventh floor to visit the apartment of a friend on the 11th floor. When she returned, she told police, she found Queen Washington’s body in the hallway.

“Both families are devastated,” the city councilman who represents the area, Charles Barron, said yesterday at the houses. “These are just two little babies. It’s just so terrible.”

When police detectives first questioned the 9-year-old, the girl, nervous and confused, told them she and the other girl had been playfully wrestling around on the floor of the apartment when the 11-year-old accidentally sustained the knife wound, police said.

Detectives from the 75th Precinct’s homicide squad weren’t convinced. While they questioned the girl further at the precinct house, detectives said, she allegedly confessed to stabbing Queen Washington with the steak knife. The reason, detectives said, was a dispute the two were having over a small rubber ball.

Late last night, lawyers for the city who were discussing the case with detectives determined that she would be charged with manslaughter, reports said

The identity of the 9-year-old girl, was not made public because of her age. She will probably be tried in family court as a minor, a spokeswoman for the city’s corporation counsel, Kate O’Brien Ahlers, said yesterday.

“This is among the youngest cases we’ve seen,” Ms. Ahlers said.