The spill has happened from the white round containers grouped on the bottom of this large zoom of the river Ambarnaya flowing from the bottom left corner towards the lake on the top.
The precise diesel images are already nicely captured by ESA:
https://www.esa.int/ESA_Multimedia/Images/2020/06/Arctic_Circle_oil_spill
But here are images grabbed from CreoDias. First the still clean green tinted stretch close to the Pyasino lake outflow to the top of the image of this small river that opens up to two paths in this image from the 23rd May. There is still some lake ice on the small ponds around the river.
Next the stretch is visible on 31st May with diesel visible.
And finally the diesel has progressed further towards the lake on 1st June. The image is just from the border of the satellite swath.
Let’s hope the diesel can be stopped before entering the lake! If you want to investigate yourself, try this link to CreoDias browser. You can play around with different channels and make their weight change in the script.
UPDATE: Planet released a very clear looking image of the extent of the oil spilled. Many small water ponds south-east of the river that flows from the collapsed tank have red content clearly visible.
Image was originally posted in this post: https://www.planet.com/pulse/clashing-eastern-superpowers-explosions-in-the-middle-east-dark-fishing-fleets-and-more/