A bipartisan group of US lawmakers traveled to Turks and Caicos to press for the release of five Americans detained on ammunition possession charges – but encountered resistance from officials on the island, the group announced Monday.

The Americans were all arrested in recent months in the British Overseas Territory, where carrying firearms is prohibited, and face up to a dozen years in prison. Each had the ammunition in their luggage “inadvertently,” the lawmakers said in a statement.

Republican Sen. Markwayne Mullin led the trip, which also was attended by Democratic Sen. John Fetterman and GOP Reps. Guy Reschenthaler, Josh Brecheen, Michael Cloud and Bob Good. The lawmakers met with Turks and Caicos officials, including the governor, attorney general, minister of tourism and police leaders, the statement from Mullin’s office said.

“Unfortunately, despite our willingness to work with Turks and Caicos officials to get our constituents home, we were not able to find a path forward today,” Mullin said in the statement. “At this point, well-intentioned American citizens are facing a dozen years in prison all for unknowingly having one or two bullets in their luggage.”

“Should they receive a prison sentence, we will need to consider additional actions to safeguard American citizens.” Mullin said.

The detained Americans have been identified as Sharitta Grier, 45; Michael Lee Evans, 72; Bryan Hagerich (no age listed); Tyler Scott Wenrich, 31; and Ryan Tyler Watson, 40.

Each is accused of bringing various amounts of ammunition to the chain of 40 islands in the tropical Atlantic Ocean southeast of the Bahamas.

Bringing firearms or ammunition, including stray bullets, into Turks and Caicos without prior permission from police is “strictly forbidden,” according to a statement from its government.

People who violate the law face a minimum 12 years in prison, the US Embassy in the Bahamas said in an April advisory. Judges can lower the minimum sentence and adjust fines when there are “exceptional circumstances,” the Turks and Caicos attorney general said in a news release earlier this month.

CNN’s Manu Raju, Fabiana Chaparro, Amanda Musa and Michael Rios contributed to this report.