Southwestern Division police arrested three Venezuelan nationals for possession of a sub-machine firearm and ammunition on Saturday.
The men, ages 20, 23 and 25, were held during an anti-crime exercise conducted in the division at daybreak.
Police said the men were found hiding in a house at Icacos Village, Cedros.
The officers searched the premises and found a Kel-Tec Sub 2000, one magazine, 264 rounds of 9mm ammunition and 87 rounds of 5.56mm ammunition.
The firearm and ammunition were stashed in a crocus bag, police said.
The three suspects were taken to the Cedros police station.
On Tuesday, 11 illegal immigrants were captured in Erin.
The arrests were made after a video was posted on social media showing people jumping off a fishing boat and wading to the shore at a beach in Erin.
The seven foreign men and four foreign women were found at a hotel in Erin.
Police said there were eight Venezuelans, one Guyanese and two Syrians.