Mexicali Mayor Jaime Diaz Ochoa said another five people were being treated at a local hospital for burns, and were in serious condition.
He said the cause of the blaze was being investigated by the state prosecutors' office.
The fire broke out early Tuesday at the nonprofit facility located in a rural area about a half-hour's drive outside Mexicali.
Diaz Ochoa said 23 residents had been taken to a temporary city shelter, and would be referred to a city elderly care center. He said most were apparently over 75 years old.
