SHANGHAI (Reuters) - Initial public offerings (IPO) on China's mainland stock exchanges may restart sooner than expected, state media reported on Wednesday, after the securities regulator ordered underwriters to update application material for firms waiting to list.

The China Securities Regulatory Commission (CSRSC) has told underwriters to complete their submissions of revised disclosure materials as early as the end of this week, the official Shanghai Securities News reported, citing multiple unnamed investment bankers.

CSRC's order concerns 32 companies that have already submitted preliminary disclosures but later changed the exchange on which they planned to list, the paper reported.

The regulator has told underwriters to update those disclosures with the latest 2013 financial statements and an explanation on why the company is changing its listing location.

CSRC told IPO applicants in January that they needed to update their application materials to reflect their latest earnings and financial positions.

Once the 32 firms that plan to change their listing location have submitted their updates, CSRC may re-start IPO approvals for the roughly 700 firms waiting to list, the paper reported.

CSRC chairman Xiao Gang said last week that IPOs had not been halted but had only paused to allow companies to update their disclosures.

China allowed IPOs to resume in early 2014 after a hiatus of 14 months, allowing around 50 already-approved companies to list on the Shanghai and Shenzhen exchanges.