Montgomery County police are investigating the death of a 1-year-old girl found on the living room floor of her Rockville home early yesterday, officials said.

Fire and rescue officials were sent to the home of Amani Renne Robinson in the unit block of Moore Drive about 8:40 a.m. for what a 911 dispatcher said was a report of an infant found dead in a bathtub.

When paramedics arrived four minutes later, they found the girl in cardiac arrest, on the living room floor, said Capt. Jim Resnick, a county fire and rescue spokesman. An unidentified babysitter also was there.

Paramedics in the first ambulance to arrive at the home said that no one had performed cardiopulmonary resuscitation on the child and that they administered "advanced life-support measures" and cardiac emergency medications. "We did not get a positive response," Resnick said.

The child was pronounced dead a short time later at Shady Grove Adventist Hospital.

A hospital spokeswoman declined to state an exact time of death.

An autopsy will be performed at the state medical examiner's office in Baltimore, a police spokeswoman said.

Homicide detectives are investigating, as is customary in unusual deaths, the spokeswoman said.