What kind of leak?

Got a call from my Missus this morning that there was a huge stain on the ground where i normally park my car. It's a e92 320d and its parked facing the door so wondering if it's from my car or another visitor who was at the house this morning. I checked my car at work and no sing of any leaks but it's parked on a slope at home and level at work.
Liking at the pics it seems to be coming from the rear end is gas tank but I don't seem to be leaking gas as I monitor my mileage the whole time.
What do ye think?

Did you just fill the tank with fuel?

i had earlier in the week..from reading on the web it's a known issue with the e90 and the fuel pipe..dropping it in next week to get the upgraded pipe installed...