Chinese authorities have released all employees of a US corporate due diligence firm detained in Beijing two years ago.

The detained Beijing employees at Mintz Group, all Chinese nationals, have been freed, a company official said on Tuesday.

News of their release came on the heels of the just-concluded China Development Forum in Beijing attended by dozens of foreign chief executives, a platform that Chinese officials had used to bring home the message that China is open to foreign capital.

"We are grateful to the Chinese authorities that our former colleagues can now be home with their families," the Mintz official said in an email.

Mintz has 12 offices around the world and more than 280 investigators, according to its website. (Reuters)