Five people, including two children, were found dead inside a South Florida home Sunday, likely victims of carbon monoxide poisoning, police said.

The body of a woman was found in a sport utility vehicle running in the garage, police said. Officers found the bodies of two children and two adults inside the four-bedroom home in southwest Miami-Dade County.

Police were investigating whether the deaths were accidental or part of a murder-suicide plot.

The identities and ages of the victims were not immediately released, pending notification of other family members, Miami-Dade Police spokeswoman Nelda Fonticiella said.

A relative of the victims had not heard from the family in two days and called police when no one answered at the door, Fonticiella said.

"Oh my God," said neighbor Feliza Thomas. "Their children were very young. They had a little white dog. We would say hello to each other all the time."

Carbon monoxide poisoning is the most common type of accidental poisoning nationwide, contributing to 40,000 emergency room visits annually in the United States. Each year, the odorless gas is responsible for about 500 accidental deaths and is used in about 2,000 suicides, according to government figures.