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LOS ANGELES -- A former elementary school teacher was arrested Wednesday in a school sexual abuse case allegedly involving at least 20 children and one adult, according to police.

Robert Pimental, 57, was arrested Wednesday and is being held on $12 million bail.

The Newport Beach, Calif., man faces eight counts of continuous sexual abuse and seven counts of lewd acts upon a child, according to a statement from the Los Angeles Police Department.

"The investigation began when several girls told their parents that they had been inappropriately touched by a fourth-grade teacher during school at George De La Torre Jr. Elementary," the statement read.

Pimental left his position with the school during the investigation, which began March 15, 2012.

"When the District first learned of the allegations, the teacher was immediately removed from campus ... Dismissal proceedings were initiated," LAUSD spokesman Daryl Strickland said in a statement. "Before the Board of Education could act on dismissal, he chose to retire."

Students' parents were told about the allegations last March within 72 hours of Pimental's removal from campus, in accordance with LAUSD policy, Strickland said.

United Teachers Los Angeles, a union that represents LA educators, said in a statment that it is "not familiar" with the allegations against Pimental, adding that after his resignation, Pimental is no longer a member of the union.

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"The allegations described are horrific," the statement read. "As teachers we have a duty to uphold the trust our students and their parents place in us."

Pimental had worked for the Los Angeles Unified School District since 1974.

George De La Torre Jr. Elementary is located in Wilmington, a largely Latino Los Angeles Harbor Area neighborhood with about 50,000 residents. The school, opened to fanfare in 2006, has about 800 students.

Anyone with information about the case was asked to contact police at 213-486-0570.