Onecall Travels (Atol 11146) and Dream World Travels (Atol 9398) failed on Tuesday (26 July).
Onecall traded via onecalltravels.co.uk and onecalltravels.com, said the CAA.
Dream World, meanwhile, traded via dreamworldtravel.co.uk, al-umrah.com, biznessclassflights.co.uk, bookholidaysonline.com, bookonlineflights.com and detltd.com.
The CAA said it was collating information from the two companies and would provide an update for affected customers shortly.
Anyone with outstanding bookings with either firm have been urged not to use Atol claims forms issued for other failures.
