Many questions remain about the circumstances that led to a 3-year-old boy's death at a Rochester Tim Hortons restaurant on Monday morning.

Here's what we know about the case.

'Horrible, unspeakable tragedy'

Rochester Police said that they received a call at 10:56 a.m. about a child missing from the restaurant at 1250 University Avenue. At 11:03, they received a second call that the child had been found in a grease trap behind the location.

Witnesses removed the boy from the trap and had started CPR by the time first responders arrived. The child was transported to Strong Memorial Hospital, but efforts to resuscitate him were unsuccessful. He was pronounced dead at 12 noon, according to RPD Investigator Frank Camp.

Evidence led police to believe that the boy fell through a plastic lid into a tank that contained used grease in a liquified form, Camp said. It was located just 6 feet from the restaurant's back door.

Investigators had not yet determined the size of the grease trap, which is typically a steel tank used to keep fats, oils, and grease out of the sanitary sewer system.

Victim not identified

At a press briefing Monday afternoon, police did not release the name of the boy who died. They confirmed on Tuesday that the child was the son of an employee at the store who was there working her shift. Police said the mother apparently had no one to watch her child.

Police also said that there would be no charges filed against the mother or any caregiver relating to the incident.

The Office of the Medical Examiner is continuing its investigation to determine a cause of death,

Monday:3-year-old boy dies after falling into grease trap at Tim Hortons

A spokesperson for Tim Hortons declined to answer questions Monday about the incident.

What is a grease trap?

When food residue washes down the drain as dishes are cleaned, water and oils mix together. If these oils aren't separated from regular sewage, “In the winter it hardens, and then it affects the infrastructure of the main sewer lines,” said Susan Gresh, owner of Biotech Drainline Services.

That’s what grease traps are designed to prevent.

Grease traps:They help protect pipes but have a dangerous side

While some smaller traps are boxes located inside or above ground, larger ones are deep underground pits that can hold 100 to 3,000 or more gallons of grease. In restaurant parking lots, they're often located underneath manhole covers.

The covers are then removed for tanker trucks to pump out the grease for disposal, Gresh said. She added that the traps are generally cleaned early in the morning when patrons and staff won't be around.

What went wrong?

The boy’s death raised a myriad list of questions about oversight of restaurant grease traps, such as the laws, rules and regulations involved in keeping them secured.

Investigators said Monday they did not know why the covering of the grease trap was not better secured.

In addition to law enforcement, investigations into deaths at a workplace can include local building departments, code enforcement and workplace safety agencies, according to a spokesman for the federal Occupational Safety and Health Administration, or OSHA.

OSHA's Buffalo office has opened an investigation into the incident. They have up to six months in which to complete their inquiry.

An OSHA spokesman couldn’t provide answers Monday to questions about prior workplace safety actions taken related to grease traps.

A spokesman for Monroe County's Department of Public Health said Monday that restaurant inspectors would not have looked at the grease trap since their purview is limited to the kitchen and food prep areas.

Work crews were at the scene of the fatal accident Monday afternoon making sure the opening was secured.

Monroe County Executive Cheryl Dinolfo, thorugh a spokesman, said on Tuesday that she intends to propose new legislation to require more secure covers on grease traps here.

Other grease trap deaths

A similar death involving a grease trap in Alabama resulted in a new state law and a lawsuit filed against businesses and government agencies connected to the incident, USA TODAY Network reported.

In 2017, a 3-year-old girl died after falling into a restaurant’s grease trap in Alabama. The trap's opening, covered with a green lid, was camouflaged in a grassy picnic area where the toddler and siblings were playing.

The lid opened partially when the toddler stepped on it and then flipped over, closing the trap and concealing her during a frantic search for her whereabouts.

The girl’s death also prompted a state law in Alabama that requires manhole-accessed grease traps to be secured by some type of locking mechanism and sturdy enough to "withstand expected loads.”

In 2018, a 5-year-old girl in Oklahoma was pulled from a trap after the crew servicing the restaurant had not properly screwed the cover back on. Her father was able to rescue her.

Earlier this year, three workers in Texas were hospitalized after falling into an underground grease trap that was nearly 10 feet deep.

SLAHMAN@Gannett.com

Includes reporting by staff writer Erin Gavie and USA Today network reporter David Robinson