Mexican President Felipe Calderon has signed a decree tightening regulations on day care centers, two years after a fire at a center in northern Mexico killed 49 children and injured 70.

Calderon says the new rules will not allow centers within 50 yards (meters) of any business or facility that presents a fire risk or other hazard.

The rules strengthen oversight and require centers to have emergency and disaster plans. It does not prohibit privately run centers, but requires them to be registered.

Calderon said Sunday the decree aims to prevent a recurrence of "the most terrible of tragedies" _ the fire at a center in the northern state of Sonora on June 5, 2009. The fire started in a neighboring state government warehouse.