New Jersey ? Six Muslim men suspected of plotting to massacre U.S. soldiers at Fort Dix were ordered held without bail Friday.

Prosecutors argued that the men, all born outside the United States, pose a flight risk. They are being held at a federal detention center in Philadelphia.

The men were arrested Monday during what the FBI said was an attempt to buy AK-47 machine guns, M-16s and other weapons.

They targeted Fort Dix, a post 25 miles east of Philadelphia that is used primarily to train reservists, partly because one of them had delivered pizzas there and was familiar with the base, according to court filings. Their objective was to kill “as many American soldiers as possible,” the documents said.

The men have lived in and around Philadelphia for years, worshipped at moderate mosques and worked blue-collar jobs installing roofs, driving a cab, delivering pizzas and baking bread.