PS 41 Crocheron in Bayside, Queens. Photo by insideschools.org.

An explosion at a Queens elementary school has led the School Construction Authority to conduct a citywide safety review of nearly 700 active construction sites, officials say.

Three firefighters and two workers suffered non-life threatening injuries in the Sept. 22 blast at P.S. 41 Crocheron in Bayside, QNS reported.

The SCA, which has a safety division, would not say what caused the explosion or provide a report on the incident involving agency contractors.

But an FDNY insider told me plumbers renovating a restroom at the school apparently left a leaking tank of acetylene — a highly combustible chemical compound used in a torch to solder pipes — inside a storage box. A fire alarm sounded at 5:49 p.m.

When firefighters tried to force open the box, it exploded.

The three firefighters and two civilians were taken to a hospital and treated for minor injuries, officials said. The 448-student K-5 school opened the next day.

The incident occurred under the watch of SCA’s newly appointed president and CEO, Celeste A. Ramirez, appointed in June by Mayor Zohran Mamdani.

Ramirez has fired several top executives in an overhaul of the multi-billion dollar agency, I’ve reported.

The new SCA chief “is committed to ensuring that all construction sites follow required safety protocols,” spokeswoman Shoshana Khan said in a statement in response to my questions.

“Following the September 22 incident, out of an abundance of caution, the SCA immediately halted work at the site and launched a citywide review of nearly 700 active construction projects, with 584 reviews completed to date.”

Khan added that site safety requirements at P.S. 41 were also strengthened to include updated fire protection plans and end-of-shift checklists for tanks on construction sites.

Work at P.S. 41 remains partially suspended pending the SCA review, she said.

“We deeply regret the injuries resulting from this incident and are taking every necessary step to ensure the safety and security of our worksites before construction activities fully resume.”