The Orange, Conn., girl is partially deaf and normally uses a hearing aid. Her hearing aid was left behind, prompting concerns among rescuers that she might not be able to hear people calling her name.
When ABC News reached Isabella's grandfather by phone Tuesday, he said that the family was "anxiously awaiting her safe return."
The girl's disappearance sparked an outpouring of support and help from the girl's hometown of less than 14,000 people.
Police enlisted the help of the FBI, fire department and police cadets to assemble a team of 100 that has fanned throughout the town of less than 14,000 people.
A prayer vigil was held Monday for Isabella by Orange Congregational Church, the church where the girl was baptized and her parents were married.
"We are part of a very close-knit community here," Orange resident Willie Ayala told WTNH.
Ayala's daughter, Andriana, is one of Isabella's classmates.
"We've just been trying to keep hope, because we know we are going to find her," Andriana told WTNH.
A candle was lit at the church each day Isabella was missing.
ABC News' Emily Friedman contributed to this report. ABC Affiliate WTNH contributed to this report.