J.P. Morgan Chase & Co. has pulled out of a $1 billion initial public offering of a Chinese chemical company and won't seek a role in the IPO of a Chinese state-owned train maker, as the bank walks away from deals that could come under scrutiny from U.S. investigators probing its hiring practices in China.

In November, the big Wall Street bank pulled out as an underwriter in the IPO of China Everbright Bank. The deal has come under scrutiny by investigators because J.P. Morgan had employed Tang Xiaoning, son of the chairman...