A significant proportion of ticket machines at metro and tram stations across the capital have stopped functioning over the past week, apparently because of the high temperatures.
The machines generally malfunctioned while trying to issue paper tickets and not during the renewal of existing electronic tickets.
It is assumed that the problem is the quality of the paper, or more specifically its plastic overlay, which the Athens Urban Transport Organization (OASA) procures from a Finnish company.
Sources at the Urban Rail Transport Company (STASY) suspect that the company's technology is perhaps not designed to endure hot Greek summers.
It is thought that the problem might not the be the machines themselves but the laminated paper which might be melting due to the heat and blocking the machine.
OASA is seeking to determine the exact cause of the problem.
Meanwhile the malfunctional machines have led to larger queues in metro stations.