A person was reported entering the river on Tuesday evening.
A recovery operation will continue in Westmeath today for a person who was reported entering the River Shannon.
The alert was raised at about 8 o'clock on Tuesday evening, at the Strand in Athlone.
Two underwater searches took place yesterday morning and afternoon, by search and recovery divers from Athlone Sub-aqua club, Longford Scuba divers and Shannonside snorkellors, as well as the Garda Sub-Aqua Unit.
Anyone who was in the area around 7.45 or 8 o'clock Tuesday evening is asked to contact Athlone Garda Station.