"Until now there was no specific deadline," Federal Office of Migrations (ODM) spokeswoman Gaby Szollosy told AFP.
The introduction of the fast-track procedure follows a "surge" in requests this summer from so-called visa-exempt countries, particularly Macedonia, Serbia and Bosnia-Hercegovina, according to the migration office.
"After speaking with reception centres we know that the majority of arrivals are Roma people," said Szollosy, who added that the measure was not aimed against one ethnic group.
Requests from Macedonia for July were up 83 percent on June, followed by Serbia (68 percent), according to the ODM.
Of 4,593 applications for asylum between January 2011 and July 2012 from Bosnia, Macedonia and Serbia only 20 were successful, the ODM said.
Nationals from these countries had "very little chance of gaining asylum in Switzerland", the ODM said, adding that these "safe countries" guaranteed minorities adequate protection against persecution.
"Nearly all these requests were unfounded and overwhelmed Swiss reception centres," said the ODM.
"No (Swiss) help can be offered to asylum-seekers who make a clearly unsubstantiated application. They must leave (Switzerland) quickly," it added.
The 48-hour procedure only applies if the application does not require any further investigation, although an appeal to the Federal Court of Administration was still possible, the statement added.