Police working on the disappearance of a 2-year-old Washington boy are now talking about switching the case from a missing persons search to a criminal investigation.

The boy's mother, Julia Biryukova, originally told police her son, Sky Metalwala, vanished Nov. 6 in Bellevue, Wash., when she left him unattended in her unlocked car after it ran out of gas.

The mother told police she walked to a gas station with her daughter and noticed the boy was missing when they returned to the car about an hour later. Police later found that there was gas still left in the car.

“On Monday we will be talking to prosecutors and will determine then if anything will happen, but that won't happen until Monday,” said Bellevue police Maj. Mike Johnson in a news conference Sunday.

There is a possibility authorities could charge Biryukova with child endangerment.

"Every hour that passes, this case becomes more and more disappointing for us that we haven't found something to lead to his discovery yet," Johnson said.

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The police previously said that Biryukova's recounting of what happened the day Sky went missing "doesn't add up."

"The public, I'm sure, is as frustrated as we are in the fact that mom isn't willing to come in and provide a polygraph...to be quite honest, that looks suspicious and we're puzzled by that," Johnson said last week.

Police said Sunday Biryukova is still not cooperating.

“But we understand that she’s traumatized by this and devastated by the loss of her son,” he said. “We’re hopeful that if she can gather herself we can have that conversation that we need to have,” Johnson added.

The disappearance of the boy occurs while his parents are in a bitter custody dispute. The boy's father, Solomon Metalwala, and Biryukova filed protection orders against each other as the pair continues with divorce proceedings.

The boy’s parents have also accused each other of abuse and psychiatric problems.