Fires occurred in the wider Browns Quay area.
A man has been arrested in connection with two suspected arson incidents in Limerick.
Gardai were alerted to a car on fire at Browns Quay at around 1:30 yesterday morning.
They received reports a number of hours later of a fire at a nearby business - with significant damage caused.
A man in his 40s was arrested in Limerick this morning and is being questioned at Mayorstone Park Garda station.
Investigators are still appealing for any witnesses to come forward.