OAKLAND -- Police are investigating an armed robbery of a "significant amount" of diamonds from a person in the Chinatown district Thursday afternoon.

Police said the crime occurred about 4 p.m. in the 200 block of 9th Street. The number of diamonds taken or their worth was not disclosed by police Thursday evening, said police spokeswoman Officer Johnna Watson.

No one was injured in the robbery. A description of the suspect or suspects was not released.

Police are asking for the public's help in the case. Anyone with information should call police at 510-238-2236 or Crime Stoppers at 510-777-8572. There is a reward of up to $5,000 for information leading to an arrest in the case.

Check back for updates.

Reach Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.