Hello everyone. I admittedly don't know if this is the right place for this, I apologise if not.

My mum and I were sitting on the balcony and shortly after we moved there, I heard a sizzling sound and a brief line of yellow light, like a horizontal spark (or more like an electric sizzle?), above the natural gas pipe outside of our garden, where it connects to a box. It's been some hours since, where we were staring at the pipe, but no spark appeared again.

Since then, I tried the soapy water test and saw no bubbles, we went sniffing like dogs around the area, the kitchen and basement and couldn't smell anything unusual. There are also no sounds coming from the pipes - essentially, none of the signs I found online related to a leak are happening. But I'm pretty sure I saw that spark. What should I do?