(Washington) The death toll from Friday’s explosion at a chocolate factory in Pennsylvania, in the eastern United States, has increased with a third death, four people still missing, rescuers announced on Saturday evening.

“Due to the violence of the explosion and the passage of time, the chances of finding survivors are rapidly diminishing,” local fire chief Chad Mayor said during a press briefing.

The investigation continues to determine the causes of the explosion, which occurred just before 5 p.m. Friday at the site of the RM Palmer Company factory in West Reading. The hypothesis of a gas leak is considered.

The factory “was almost flattened, unfortunately. There is not much that can be salvaged from the building,” local mayor Samantha Kaag warned on Friday.

According to its website, RM Palmer had been producing chocolates at this factory since 1948 for celebrations such as chocolate bunnies for Easter or chocolate hearts for Valentine’s Day.