A man and woman are being held on suspicion of possessing a prohibited weapon.
Two people are in police custody after an incident in Gorseinon which saw people evacuated from their homes.
Armed officers and bomb disposal units were deployed to Trinity Street yesterday afternoon as a precaution after reports of a domestic disturbance.
A 41-year-old man and a 39-year-old woman are being held on suspicion of possessing a prohibited weapon.
The man was also arrested on suspicion of causing criminal damage.
Residents were allowed back in their homes yesterday evening and a cordon to prevent entry to the street has now been lifted.
The public - and in particular local residents temporarily displaced from their homes - are thanked for their cooperation and patience during the incident, allowing officers to ensure their safety.