55 year old Michael O'Leary from Nantgaredig hasn't been seen in almost a week.
Police have released pictures of a car belonging to a missing man from Carmarthenshire.
Searches for 55 year old Michael O'Leary from Nantgaredig are continuing as officers releasing the image of his silver Nissan Navara as part of efforts to trace him.
He's not been seen since Monday 27th January.
A 52 year old man from Carmarthen is being questioned by police on suspicion of murder.
Detective Chief Inspector Paul Jones said: "A very thorough, and fast-paced investigation is taking place to establish the circumstances around Mr O’Leary’s disappearance.
"We are considering all the facts and evidence in front of us, which at this time includes questioning a man who might have vital information that could help us.
"We are particularly interested in identifying anyone who has seen Michael O’Leary’s vehicle, which is a silver Nissan Navara between Cwmffrwd and Capel Dewi between 8pm and 10pm on Monday, January 27, 2020 or from anyone with information who was in this area during these times.
"We understand the latest development might create concern in the community, but we would like to reassure that we are doing all we can to find answers for Mr O’Leary’s family.
"We ask that anyone with information contacts police urgently."