An undercover operation by the Department of Homeland Security found that Transportation Security Administration screenings fail to spot weapons more often than not.

The investigators found that they were able to get through airport security checkpoints with mock knives, guns, and explosives at an alarmingly high rate. According to an ABC News source, the failure rate is “in the ballpark” of 80%. Faults were due to screeners, their equipment, or their procedures.

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The House Committee on Homeland Security was privately briefed on the matter on Wednesday. In a public hearing following the briefing, members of Congress called the report “disturbing.”

The DHS’s Office of Inspector General reportedly made eight classified recommendations based on the operation. In response, the TSA has said that it takes the findings “very seriously” and will be implementing measures that “will improve screening effectiveness at checkpoints.”

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The TSA has already launched a pilot program using CT scanners and last week announced an additional $4 million investment in the new technology.

While an 80% failure rate is disconcerting, it is actually an improvement on years past. Just two years ago, a similar undercover investigation found a 95% failure rate, reports CBS News.