The HSE was strongly advised by the Department of Agriculture to stop using ViraPro hand sanitiser more than a fortnight before it was recalled from health facilities and schools.
Documents obtained by RTÉ News show a Department of Agriculture official emailed the HSE to "strongly advise removing all ViraPro Sanitiser Product you currently have in use in the HSE" on 7 October.
However, it was more than two weeks later, on 23 October, before the HSE formally issued a recall notice to tell its health facilities to stop using the product.
The documents, released under the Freedom of Information Act, also show the HSE was first alerted to an issue with the product on or before 29 September, almost a month before the recall.
In a statement the Department of Agriculture said that initial advisory was made, only to the HSE, after it received preliminary test results on samples of the HSE's supply of ViraPro.
A HSE statement said after the initial advisory from the Department of Agriculture it quarantined all stock and verbally agreed to take no further action until test results were available. When they were, it said it acted in a timely and appropriate manner.
But unions say this episode highlights the many questions they have about the HSE's handling of the ViraPro issue.
SIPTU's Assistant Secretary General, John King, said the delay in informing health workers was unacceptable and demonstrated what he said was the HSE's "blasé" attitude to the issue.
He said unions meet weekly with the HSE to discuss Covid-19 and it was "disappointing" that the potential issues had not been flagged with employee representatives at an earlier stage as he said healthcare workers would have been required to use the product numerous times an hour during a single shift.
The INMO has said they have requested specific information from the HSE about the areas affected by the ViraPro issue.
INMO General Secretary Phil Ní Sheaghdha said the safety of healthcare staff had to be priority number one.
"Without safe healthcare staff we won't be able to provide care for those who need it," she said.
Issues with the ViraPro sanitiser first came to light on 22 October when schools received an alert from the Department of Education to stop using the product, just before they were due to wrap up for the mid-term break.
Tests showed the product contained methanol rather than ethanol and the Department of Agriculture warned prolonged use of the product could cause dermatitis, eye irritation, upper respiratory system irritation and headaches.
The following day, the HSE also issued a recall notice to all health facilities as it had ordered 3.7 million units of the product at a cost of €7.5m.
At the time, the Minister for Agriculture said he was not made aware of the issue until the same night that schools were alerted and that he had ordered an investigation into why he had not been alerted sooner.
But copies of emails exchanged between the HSE and the Department of Agriculture show the department was aware of the issue almost a month before and advised the HSE to stop using the product more than two weeks earlier than it was withdrawn.
On 29 September, a member of the HSE's procurement team contacted an official in the Department of Agriculture, with the email saying "follow up on the ViraPro issue".
On 7 October, the Department of Agriculture official emailed the HSE to inform them that the department would be issuing detention notices to the HSE warehouses storing the ViraPro product.
They added: "In the meantime, I strongly advise removing all ViraPro Sanitiser Product you currently have in use in the HSE."
A detention notice was issued by the department on the following day, 8 October.
But it was more than two weeks later before the HSE formally issued a recall notice.
On the afternoon of 22 October, the Department of Agriculture emailed the HSE to notify it that ViraPro sanitiser had been removed from its biociodal product register with immediate effect.
It said it was no longer legal for use or sale in Ireland and should be removed from circulation with immediate effect. The HSE issued its recall notice the following day.
At the time, the Department of Education said it was first notified about the removal of the ViraPro product from the Department of Agriculture register by phone two days before it issued its alert to schools.
But it said when it was first alerted "details of the issues and public health concerns arising were not available at that point".
Sinn Féin's health spokesperson has said it was "incredible" that the HSE took two weeks to issue a recall notice.
David Cullinane has called on the HSE to explain what he described as a "delay in taking decisive action".
He said: "This new information again exposes poor communication between the Minister for Agriculture and his department and a failure to take more urgent action by [the] HSE on such an important issue."
Labour's education spokesman Aodhán Ó Ríordáin said they are still awaiting answers from what he described as the ViraPro "debacle".
He said it was "depressing" and "not good enough" that different government departments were not communicating effectively in a pandemic.