Federal law enforcement officials say two men arrested Friday, now held on gun charges, are suspected of trying to acquire pipe bombs with the intent of using them during protests in Ferguson, Missouri.

Two officials say the men claimed to have affiliations with the New Black Panther Party and were trying to acquire guns and explosives. When investigators heard about their plans, they placed the men under surveillance. "We wanted to see where this might go," one official said.

Court documents say the two men, Brandon Orlando Baldwin and Olajuwon Davis, were arrested after they made false statements while trying to buy two pistols at a sporting goods store in Hazelwood, Missouri. They currently face only the firearms charges, though officials say other charges are pending.

Another federal official said the two did not appear to constitute a very serious threat and that there was no indication they were part of a larger operation. The St. Louis region — and other cities across the country — are preparing for potential protests as a grand jury decides whether a police officer who fatally shot unarmed teen Michael Brown will be charged. The decision could be announced any day.

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