Drilling into what looks like brick - hit a blocker almost immediately

[mgrcpab]

Hi all, drilling into what looks like a brick wall in our cellar, to hang something up, but after around 5mm the drilling just stops, with both normal and masonry drill bits. I used a stud finder and metal/wires finder and they both said nothing was there in the area. I’ve attached an image of what I’m looking at, again it looks like brick but doesn’t go very deep, and there’s maybe sign of a different material in the middle at the back of the hole. Any ideas on what could be going on and what to do next? Cheers!

 

[Alec_t]

It looks like the head of a rusted Phillips screw? If so, it's strange your metal finder didn't detect it.
Let's hope it isn't a gas pipe!

 

[JohnD]

Chip away the plaster and have a look.

 

[blup]

It could be a non ferrous/magnetic metal, maybe a copper core that supplied a circuit or acted as a incomer.

Blup

 

[foxhole]

Move the hole 10mm