(Reuters) – A U.S. judge on Tuesday blocked the planned release of 3-D printed gun blueprints hours before they were set to hit the internet, siding with states that sued to halt publication of designs to make weapons that security screening may not detect.

U.S. District Judge Robert Lasnik in Seattle said the blueprints’ publication could cause irreparable harm to U.S. citizens. The decision blocked a settlement President Donald Trump’s administration had reached with a Texas-based company, which initially said it planned to put files online on Wednesday.

Gun control proponents are concerned the weapons made from 3-D printers are untraceable, undetectable “ghost” firearms that pose a threat to global security. Some gun rights groups say the technology is expensive, the guns are unreliable and the threat is being overblown.

Josh Blackman, a lawyer for the company Defense Distributed, said during Tuesday’s hearing that blueprints had already been uploaded to the firm’s website on Friday.