Gripped by a 10th straight day of 100-degree heat, California sweated out the possibility of more blackouts Tuesday as the number of suspected heat-related deaths climbed to at least 56 and the rotting carcasses of thousands of dairy cows and other livestock baked in the sun.

Some communities faced their third day without electricity as the record-breaking temperatures strained transmission equipment.

The stretch of 100-plus-degree scorchers that descended on the state last week marks the first time in 57 years that both Northern and Southern California have experienced extended heat waves simultaneously, California Undersecretary for Energy Affairs Joe Desmond said.

Coroners in 13 counties were investigating deaths that appeared heat-related. Most of the victims were elderly. Among the dead was a nursing home patient in Stockton who died after the air conditioning gave out in 115-degree weather. A gardener collapsed on the job and died. A woman was found dead along a bike path.