Armed police swooped on a residential area in Gorseinon on Thursday morning.
Officers from South Wales Police were called to Tredegar Road on Thursday morning and remained there for several hours.
There were a number of police vehicles at the scene, including both cars and vans.
Officers were seen knocking on doors in the area as they appeared to be carrying out house to house enquiries.
This comes after armed police were called to Trinity Street in Gorseinon in the summer after a man had "barricaded" himself inside a property. Officers were seen using "smoke bombs" at the scene in July.
While the two incidents aren't related, residents in the area have voiced their concern.
A neighbour said: "I walked past and saw loads of police - it stopped me right in my tracks. It was even more of a shock to see that some of the officers were armed.
"I don't know what it was about, but it is very concerning. There was a massive police presence just around the corner a few months back. I hope that police with guns isn't going to be a regular occurence."
South Wales Police has been asked to comment.
