LAKELAND, Fla. -

Two toddlers found in their grandparents' swimming pool have died, authorities said Sunday.
    
Eighteen-month-old Silas Lugo-Walsh was pronounced dead Saturday at 11:03 p.m. His 2-year-old cousin Jayvien Watkins was pronounced dead about an hour and a half later on Sunday, the Polk County Sheriff's Office said.

Deputies had said the boys were in extremely critical condition after being rescued from the pool at their grandparents' Lakeland home Friday evening.
    
The cousins had been missing for about 10 or 15 minutes before family members realized they were gone, investigators said. The relatives began searching frantically for the children and found them face down in the pool.
    
Rescuers flew both toddlers to a Tampa hospital.
    
"You know, this breaks all of our hearts," Polk Sheriff Grady Judd said after the boys were hospitalized. "If it's not bad enough that it's occurring, it's occurring on the weekend of Mother's Day where we celebrate with our children and our grandchildren. This is a nightmare of monumental proportions."
    
Judd called the incident a "tragic, tragic accident."
    
The pool had a fence around it, but the gate appeared open. The house's back door also has a latch that can be easily pushed open, Judd said.
    
The investigation is ongoing. Autopsies will be conducted on both boys.