Authorities launched a manhunt and issued an amber alert Wednesday for a pregnant woman who allegedly kidnapped her six children from her estranged husband's San Leandro, Calif., home and stole his van during a supervised visit.

The search is on for Enja Moore, 33, who is homeless and living in the Hayward, Calif., area, according to Alameda County Sheriffs Sgt. J.D. Nelson.

Just before midnight during a supervised visit, the father found that his estranged wife, six kids and van were all missing, Nelson told FOX News. He'd been in another part of the house when the children and his wife disappeared.

Authorities are concerned about the health of the 3-year-old boy, who needs insulin three times a day. Police don't think Moore has insulin with her.

Authorities believe the mother, who they say is nine months pregnant, is in the Hayward area with the car, which is likely low on gas.

An amber alert was issued in the San Francisco Bay area after the vehicle’s license plate number was confirmed, police told FOX News. The alert is not statewide.

Click here to read more from KTVU TV in San Francisco.