The Independent Commission Against Corruption (ICAC) has raided the headquarters of the New South Wales Labor Party in Sydney.

Key points: Senior Labor officials were at a conference in Adelaide, many said they were surprised by news of the raid

Senior Labor officials were at a conference in Adelaide, many said they were surprised by news of the raid The ABC understands the raid was related to a fundraising event called the Chinese Friends of Labor

The ABC understands the raid was related to a fundraising event called the Chinese Friends of Labor The investigation relates to wealthy individuals attempting to circumvent the political donation cap

Staff from the corruption watchdog arrived at the party's Sussex Street headquarters on Tuesday looking for documents relating to an ongoing investigation into ALP donations.

The ABC understands officials were searching for financial documents linked to an annual party fundraising event called the Chinese Friends of Labor.

The investigation relates to a political donation made by a property developer in 2015 — the Labor Party has banned political donations from property developers.

Sources told the ABC the donation relates to wealthy individuals attempting to circumvent the $2,000 cap on political donations in NSW.

However, the exact reason for the raid is still unclear.

A listing on the NSW Labor website selling tickets for the Chinese Friends of Labor annual fundraising dinner in 2017 had a table of 10 for $990 and a VIP table of 10 at $2,500.

Chinese-media coverage of the Chinese Friends of Labor show the group holds numerous fundraising events and dinner functions throughout the year.

Several senior Labor officials were at the 2017 Chinese Friends of Labor fundraising dinner. ( Facebook )

Senior Labor members such as Chris Bowen, former opposition leaders John Robertson and Luke Foley, former senator Sam Dastyari and member for Kogarah Chris Minns have been seen at these events.

The ABC is not suggesting any of the individuals are the subject of the ICAC investigations.

All senior Labor officials, including NSW ALP boss Kaila Murnain, are at the party's national conference in Adelaide, which finished on Tuesday, and were not present during the raid.

When the ABC contacted senior NSW Labor officials, many were surprised by the news of the raid.

The NSW Labor Party later released a statement in response to the investigation.

"The donations in question were received in 2015 and have been fully investigated by the NSW Electoral Commission with the full cooperation of NSW Labor, including the provision of all relevant documents," a NSW Labor spokesperson said.

The Electoral Commission referred the ABC to ICAC, which has declined to comment on the matter.