A search is due to resume at first light on Wednesday on a canal near the Ardnacrusha power station in Co Clare following a report that a body part was seen in the water.
A motorist passing over a bridge near the power station reported seeing an arm sticking out of the water around 4.30pm on Tuesday.
Three units of the Limerick City and County Fire Service were dispatched to the scene, along with the Shannon-based Coast Guard 115 rescue helicopter, and seven members of the Kilaloe-based coastguard marine rescue service.
Limerick Marine Rescue Service divers remained at the scene until shortly after 9pm but nothing was found in the water.
A ripped blue coloured t-shirt was discovered on the bank of the canal but it is unclear whether it has any evidential value.
The hydroelectrical power station at Ardnacrusha switched off its turbines which are located in the canal to aid the search operation.
“We will be resuming searches in the morning,” said a Limerick Marine Rescue Service spokesperson.