The U.S. Food and Drug Administration is warning a Massachusetts school over its use of a controversial skin-shock therapy with students who have disabilities.

In a letter sent to the Judge Rotenberg Educational Center earlier this month, FDA officials said the devices used to administer electric shocks at the school “violate the Federal Food, Drug, and Cosmetic Act (Act) because your facility has failed to obtain FDA clearance or approval.”

The school, which serves children with developmental disabilities as well as those with behavioral and emotional problems, has come under fire for years from disability advocates who say that using electric shocks to address behavior issues is inhumane. However, some parents and former students have defended the school arguing that the approach is effective.

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The FDA warning comes following an October inspection of the Canton, Mass. center. Federal officials said that if prompt action is not taken to correct the violations, the school may be subject to “seizure, injunction and civil money penalties.”

In a statement to ABC News in response to the FDA letter, officials at the Rotenberg Center said they plan to meet with the FDA in January and indicated that they are working with the agency to address the concerns.