Germany's coronavirus app for tracking infections wasn't working properly for up to five weeks due to an issue affecting millions of Android and Apple devices, German media have reported.

Initially, the Bild daily newspaper said users of Samsung and Huawei phones, among others, weren't sent an alert if they had come into contact with someone infected with COVID-19. 

The issue was confirmed by the Health Ministry, which admitted that some Android operating systems had blocked the app from running in the background in order to save power. 

Read more: Day one of using Germany's coronavirus tracing app

No warning that app was defective

"There was indeed a problem with earlier versions of the Corona-Warn-App in terms of background updates on Android devices," a spokesman for the SAP software manufacturer, which worked with the German government to develop the app, told Bild on Friday. The ministry said the issue has since been fixed.

Later Friday, the Tagesschau news site reported that a similar problem had been experienced by iPhone users.

"There are problems, and I very much hope that they will either be resolved very, very quickly or that we will find an effective workaround to get the functionality up and running," said Thomas Klingbeil from SAP. "The problem we have is that the background update does not appear to be called by the operating system."

Tagesschau said developers had informed Apple about the issue, and said the tech giant had acknowledged a bug in the iOS operating system. 

Germany's coronavirus tracing app works by exchanging anonymous codes with other smartphone users who come within 2 meters (6.5 feet) for a period of 15 minutes or longer.

When someone notifies the app they have tested positive for COVID-19, a notification is sent to those who have been in that individual's vicinity. 

Those codes are swapped whether or not the app is running in the background. But if the background update function is disabled, notifications about a potential infection risk cannot be sent out. Affected users would then only be warned if they open the app.

Read more: Mandatory COVID-19 tests urged for returning German holidaymakers

Call for transparency on COVID-19

Jens Zimmermann, the center-left SDP's spokesperson for digital policy, called for "a swift explanation" from Health Minister Jens Spahn.

"It is more than annoying that the responsible politicians are hearing about this matter from the media," he told Reuters news agency. "I would have liked to see open communication from the Health Ministry."

In its statement, the ministry stressed that the problem was with Android settings, which can impact any app. It said the problem had been solved with a new version of the app released on Wednesday.

The RKI reported in mid-July that the voluntary tracing app had been downloaded around 16 million times since its launch in mid-June.

German authorities are hoping the tool will help better trace the virus and break chains of infection as cities lift restrictions and return to normal life.

Germany has so far registered more than 205,000 coronavirus infections and 9,120 deaths, according to statistics compiled by Johns Hopkins University.

nm/mm (Reuters, AFP)