Work has been suspended on board one of ExxonMobil's drilling rigs off Nova Scotia after a heavy chain fell near workers.

Five workers were on the deck when a 16-metre, 102-kilogram chain with a shackle fell. No one was injured.

The Canada-Nova Scotia Offshore Petroleum Board said the incident happened Nov. 5 on the Noble Regina Allen rig, which is decommissioning wells for the Sable Offshore Energy Project.

Work stopped immediately and operations remain suspended, the board said Thursday in a news release.

"It was determined that it had the potential for fatality, and has thus been classified as a high-potential near miss," said the board.

ExxonMobil and Noble Corporation, the owner of the rig, are investigating the incident.