The United States Food and Drug Administration (FDA) has said that it can find no link between Tamiflu and the deaths of 12 Japanese children who took the drug.
But its European counterpart EMEA and the Swiss Agency for Therapeutic Products, Swissmedic, are still looking into the anti-viral's possible side effects.
Tamiflu is manufactured by Swiss pharmaceutical giant Roche and is in high demand as a defence against a possible avian flu pandemic in people.
The FDA said the 12 deaths it was reviewing included one suicide, four cases of sudden death and four cases of cardiac arrest. There also were single cases of pneumonia, asphyxiation and acute pancreatitis.
"Based on the information available to us, we cannot conclude that there is a causal relationship between Tamiflu and the reported paediatric deaths," the FDA said on its website on Friday.
Linda Lewis, an FDA medical officer, said there was "insufficient evidence to establish that deaths and neuropsychiatric events represent a safety signal associated with Tamiflu".
The FDA had earlier reported that it had been "concerned" that 32 psychiatric events, such as hallucinations and abnormal behaviour, had also been reported in children who took Tamiflu. All but one of the cases were reported in Japan.
The "most alarming" psychiatric events, according to the FDA, included two cases in which two children jumped out of the second-floor windows of their homes after receiving two doses of Tamiflu.
The agency said that it would continue to study the potential side effects of the drug in patients of all ages and report back within two years.
The FDA's European counterpart, the European Medicines Agency (EMEA), said it was also studying the possible side effects of Tamiflu. It was reported on Friday that it had asked Roche to provide it with more information on any possible issues linked to the anti-viral.
There have been two cases of "presumed suicide associated with the medication", the EMEA said.
On Friday Swissmedic also announced that it had requested information from Roche on links to possible neuropsychiatric effects of the drug.
But the agency that it would only make a decision on whether to withdraw Tamiflu after it had evaluated the data.
Interest in Tamiflu has risen as experts around the world warn of the possibility of an H5N1 bird flu pandemic among humans. Several countries are stockpiling the drug, which may be able to lessen symptoms.
This week Roche subsidiary Chugai Pharmaceutical told the Japanese government that two teenage boys had shown abnormal behaviour that led to their deaths after taking the drug.
But Roche said several studies in the US and Canada had shown that the incidence of death in influenza patients who took Tamiflu was far lower than in those who did not.
"The benefit/risk ratio for Tamiflu is unchanged and remains positive," said Joseph Hoffman, Roche vice president for pharmaceutical development.
swissinfo with agencies
Tamiflu was invented by Gilead and licensed to Roche in 1996.
The oral treatment has proven effective against influenza A and B and the avian H5N1 strain of influenza currently circulating in the Far East.
In preparation for a possible bird flu pandemic, governments are stockpiling the drug. So far Roche has received bulk orders from around 50 countries.