Microsoft has finally started rolling out the Windows 10 Mobile update to Lumia 640 in Europe. David Ramos/Getty Images

Past rumors indicated that the Windows 10 Mobile OS will be rolled out starting Jan. 12. But then, as we know, it didn’t materialize. Now, a new report said that Microsoft has started rolling out the latest firmware to handsets running the Windows Phone 8.1 OS in Europe.

The users of Microsoft Lumia 640 in Poland are now receiving the Windows 10 Mobile update from T-Mobile. T-Mobile Poland has reportedly confirmed the new software version as “02177.00000.15184.36002.”

Polish Lumia 640 users under T-Mobile network can now check the availability of the updates via handset’s settings. In any case, device owners should note that, the carrier is apparently sending out the firmware in batches to reduce the burden on Microsoft's servers, Neowin noted. Therefore, it could take a couple of days before everyone receives a notification.

T-Mobile Germany, on the other hand, had listed the first batch of eligible Lumia devices. The list includes the Lumia 535, Lumia 635, Lumia 640 LTE, Lumia 640 XL, Lumia 830 and Lumia 930. The aforementioned handsets came with Windows Phone 8.1, straight out of the box.

Even though, the compatible devices were listed on Jan. 4, the carrier says, it could “take up to 2 weeks until the manufacturer provides the update on its servers. Updates are released at the beginning in spurts so that the servers are not overloaded.”

Other reported eligible old Lumia handsets include Lumia 735, Lumia 630, Lumia 520, Lumia 532, Lumia 625, Lumia 720, Lumia 820, Lumia 920, Lumia 925, Lumia 930, Lumia 1020 and Lumia 1320. In any case, readers should note that, this is not the comprehensive list. But these devices are earmarked to receive the Windows 10 Mobile update at some point in 2016.