A fire broke out but it was too early to say whether production had been affected, the source said.
The pipeline was attacked in December, causing a loss of production estimated at between 70,000 barrels a day and 100,000 bpd.
The fire broke out 21km from North West Marada, NOC roughly the same area of the December attack.
The area is frequented by Islamic State fighters, Libyan officials have said.
NOC said its firefighters were at the site.