Police are searching for two young girls last seen in Brevard County. Investigators said their parents have threatened to kill the girls and themselves.

Police say the couple's desperation over one daughter's autism seems to have pushed them to a breaking point.

Police are looking for 2-year-old Kiah and 4-year-old Kristen Firth. Kristen has autism, according to police.

Police said James and Mai Firth, parents of the girls, made a suicide pact to kill their children and themselves if their money for their daughter's autism treatment ran out, or if their daughter didn't show progress during treatment.

The family lives in Vietnam but came to the United States to get treatment for their daughter, police said.

Investigators say James Firth lied to police about which hotel they were staying at in Melbourne during the child's treatment, then disappeared with the family on Thursday.

Melbourne police say the family is in a silver 2002 Lexus SUV, with Florida license plate 612PGW. Police released a photo of a similar SUV on Friday.

Police said the family was last seen near the Florida Institute of Technology in Melbourne Thursday.

James Firth has family in Ormond Beach, Michigan and Arizona. Police believe they could be headed to any of those areas. Investigators said it is also possible the family may be traveling to San Francisco to get on a flight to Vietnam.

Anyone with information about this family's whereabouts is asked to call Melbourne police or Crimeline at 1-800-423-TIPS (8477).