A former Los Angeles-area elementary school teacher has been charged with lewd acts on children, including putting cockroaches on students' faces and offering them a spoonful of what may have been semen, authorities said on Tuesday.

Mark Berndt, 61, was arrested at his home in the Los Angeles suburb of Torrance on Monday, accused of abusing nearly two dozen boys and girls, ages six to 10, between 2008 and 2011, officials with the Los Angeles County Sheriff's Department said.

Authorities began investigating Berndt over a year ago, after more than 40 photos depicting children in classrooms with their eyes blindfolded and mouths covered with tape were turned over to police, Sheriff's Department officials said.

The details on this particular case are disturbing. There's no such thing as normal and this is way beyond normal, said Sheriff's Lieutenant Carlos Marquez, who supervised the case.

Some photographs showed girls being offered a blue plastic spoon that contained a clear or white substance, which authorities now believe may have been semen.

Early in the investigation, detectives recovered a similar blue spoon from the trash within the teacher's classroom that tested positive for semen, Sheriff's Sergeant Dan Scott of the special victims unit said.

Berndt's DNA was found to match that of the DNA profile found on the spoon, he added.

In some photos, Berndt was seen with his arm around children or his hand over their mouths, Scott said. In others, children were seen with large, live Madagascar-type cockroaches on their faces and mouths, the Sheriff's Department said.

390 PHOTOS

Investigators have discovered a total of 390 photos in the case, and about 10 of the children depicted in the photos have not been identified, the Sheriff's Department said.

The original group of photos turned over to detectives came from a company that does photo processing, such as the services offered at a typical drug store, Marquez said. Investigators did not name of the company.

Investigators also recovered a DVD from Berndt's home depicting adult sexual bondage activity that mirrored the bondage-type photos of the children, Sheriff's Department officials said. The adults in the bondage video were not identified and the images in that video are not a crime.

For over 30 years, Berndt taught at Miramonte Elementary School in the Florence area of Los Angeles County, Scott said. Berndt was fired by the Los Angeles Unified School District in March 2011, shortly after the investigation began, Scott said.

The children named as victims in the case were students at Miramonte, and some were in Berndt's class, Marquez said.

The investigation involved interviews with more than 80 current and former students and school employees, officials with the Sheriff's Department said.

While this investigation took a year, we need to be very solid on these cases when you're dealing with lewd acts against a child, Scott said.

An attorney for the former teacher could not be reached for comment.

Berndt was formally charged on Monday with 23 counts of lewd acts upon on child, court records show, and was being held in jail in lieu of $2.3 million bail. He could spend the rest of his life in prison if convicted on all counts.

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