CALGARY -- The National Energy Board is expanding a safety advisory and draft order on unreliable pipeline fittings after learning of more suppliers with quality issues.

The draft order requires companies to verify whether they have any components not meeting specifications, and to file a timeline and plan to address any issues within 60 days.

The regulator says it also plans to hold a technical workshop in June on quality assurance for the pipeline components as the number of cases rise.

The latest advisory by the NEB names South Korea-based TK Corp. and India-based Tecnoforge as having in some cases supplied fittings that didn't meet material requirements, after identifying Canadoil Asia and Ezeflow Fitting in an advisory issued in February 2016.

The issue with TK Corp. was originally identified by a provincially-regulated operator in 2012, but the Tecnoforge flaws were only discovered last August by a pipeline company before installing the part.

Further investigation found the Tecnoforge fitting had been over-tempered and was weakened in some areas, and that the cause of the problem could happen with other manufacturers as well.