BELMONT -- Several containers of explosive materials were found in a Belmont elementary school field Wednesday morning, police said.

Police received a call around 8 a.m. from Belmont-Redwood Shores School District staff reporting several small plastic containers that appeared to have blown up in a field at Nesbit Elementary School, located at 500 Biddulph Way.

Officers requested assistance from the San Mateo County Sheriff's Department bomb squad, which collected the containers and concluded they had been filled with substances that had caused an explosive reaction.

No one was injured and no damage was reported.

Sheriff's detectives were already investigating two other incidents involving "acid bombs" found Tuesday night and Wednesday morning less than half a mile apart near Redwood City.

Each incident involved an object that contained multiple ingredients which together cause a chemical reaction, sheriff's officials said. No determination had been made as to whether those two cases were related.

Anyone with information about any of the incidents is encouraged to contact sheriff's Detective Saul Lopez at (650) 363-4347 or to call the anonymous tip line at (800) 547-2700.