FRESNO, Calif. (AP) — Authorities in central California say it appears a 9-month-old boy strangled himself on unbuckled car seat straps while his mother was taking a nap.

The 33-year-old mother put her son in the car seat in her room inside a Fresno apartment on Monday. Police tell the Fresno Bee (http://bit.ly/1u0Dv9Z ) that she put the straps over his shoulders, but she didn’t fasten them to a buckle between his legs.

Investigators believe he squirmed out of the seat and strangled himself on the straps while his mom slept. The mother’s boyfriend came home to find the boy blue and not breathing. The baby was pronounced dead at a hospital.

Police are continuing to investigate the incident and say neither the mother nor her boyfriend has been arrested.

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