"It takes quite a lot to get through them. I think it's only happened three times in 10 years, across our entire network.
"It's really unfortunate, but it's just one of those things."
The incident happened on Parkes Ave around 3.30pm, and affected the St Johns Hill and Otamatea areas of Whanganui.
What was "generally done" after incidents like this was the overlay of a brand new duct, Riley said.
"The hard bit is actually splicing all the fibre cables," he said.
"There are 144 single fibres in each cable, and there were two cables impacted, so that's 288 re-spliced fibres.
"That takes a lot of time. In this case, the whole incident, from start to finish, took around about 30 hours.
"It's very skilled, technical process. Basically, you're melting and re welding glass together 288 times and getting a perfect match."
No contractors or members of the public were injured in the incident and Riley said the cables were fixed overnight on Saturday and internet was restored on Sunday morning.
"Of the 660 impacted customers, there are still 22 that are not consuming broadband.
"That probably means they've switched off their [Optical Network Terminal] inside their house.
"When your broadband goes out you obviously go on a hunt to work out whether it's the router, or the box in garage. Sometimes they'll unplug it or switch off.
"We know which premises they are, so our crew is just going to politely knock on the door and let them know that the fibre is back on."
