Many M1 customers were cut off from the Internet on Monday morning, with most of the complaints coming from 3G users.
M1 acknowledged the problem at about 9.30am with a Facebook apology saying access was "intermittent" for mobile data. The telco updated customers with another posting at 1pm saying its engineers were "working hard to resolve the issue" and more updates would be provided when it has additional information.
For some affected customers, the problem started as early as 1am on Monday. They could not surf the Web or use some of the apps in their smartphones, say, for taxi booking. But they could still make calls and use the SMS function.
It is not known how widespread the problem is.