The disappearance of a woman, her two small daughters and her boyfriend in a small Alaska community is puzzling investigators.

Rebecca Adams, her two daughters Michelle Hundley (5) and Jarraca Hundley (3) and her boyfriend Brandon Jividen disappeared around May 27th.

They live in a home in Kenai, a coastal community of about 7,300 residents 105 kilometres south-west of Anchorage.

Cars belonging to Mr Jividen (37) and Ms Adams (22) remain parked at the home - and their mobile phones have been turned off.

The family apparently left behind clothes, outdoor gear and the car seats for the children. Their brown and white English springer spaniel named Sparks is also missing.

In the latest development, police want to question Ms Adams' former mother-in-law to seek information about the family.

Lisa-Marie Hundley, grandmother of Ms Adams' daughters, was held in Tennessee on an unrelated drug offence and is expected to be sent back to Alaska.

The family were last seen in Kenai

Local TV station KTUU and other reports said Hundley (46) was not believed to be connected with the disappearance but police hope to gain insightful information about the family.

The father of her two girls, Jaramiah Hundley, died in a motorcycle crash in May 2012.

The family's disappearance has now sparked a State-wide search.

Police and the FBI have searched with a helicopter and all-terrain vehicles in a wooded area near Adams' home. The family lives in a four-plex near the Wildwood Correction Facility and they failed to pay the rent this month.

Besides local police and the FBI, fire officials, canine units and wilderness search groups from across Alaska have been brought to Kenai to help search.

Police have also appealed for information on the family's possible whereabouts.