WASHINGTON (Reuters) - The son of a U.S. government chemist charged in an insider trading case pleaded guilty on Thursday to an unrelated charge of possessing several child pornography that included hundreds of graphic sexual images.

Andrew Liang, 26, pleaded guilty in a federal court in Maryland to the one count of child pornography possession for downloading at least nine videos, some of which he obtained from Japanese Internet sites.

The videos included more than 600 visual images of sexually explicit conduct involving children ranging in age from 4 to under 18, according to the plea agreement and statement of facts filed in federal court.

Liang and his father, Cheng Yi Liang, have also been charged with engaging in insider trading with information from the Food and Drug Administration about upcoming drug approvals, making at least $2.27 million from trades.

Securities regulators have said there were more trades and that the father earned more than $3.77 million in profits and avoided losses.

The two have also been close to reaching plea agreements in the insider trading case as well, court records have said previously.

Depending on Andrew Liang's criminal history, he could face anywhere from four years and three months to a maximum of 10 years in prison on the child pornography charge. He will also be required to register as a sex offender.

He is due to be sentenced on December 9.

(Reporting by Jeremy Pelofsky; editing by Mohammad Zargham)