Government raids on Crown Resorts' offices in China have sent the company's share price plummeting nearly 14 per cent on Monday, cutting billionaire James Packer's paper wealth by about half a billion dollars.

At least eighteen Crown employees, including three top Australian executives, have been held since Chinese police executed a series of late-night raids at their homes across several mainland cities on Thursday. The company, consular officials and families have been unable to make contact with the group.

Stock analysts are scrambling to figure out the ramifications of the Chinese crackdown on the Australian casino operator's earnings, with initial estimates suggesting about 5 per cent could be wiped from its profit.

Crown shares closed down 13.9 per cent for the day at $11.15.