DEVELOPING: Police are investigating a suspicious white powder that was sent to the offices of The New York Times.

The newspaper told employees that the substance was found Wednesday morning when an employee opened a letter on the 13th floor of company headquarters in midtown Manhattan. Police were called to the scene and are investigating to determine if the substance is harmful.

"There is an investigation going on at The Times building right now, but these things are a dime a dozen, and it is too early to give out any more information," the NYPD told FOX News.

The newspaper closed one lobby to the building, but said it was still allowing people to come and go through other exits after the discovery.

The discovery comes after more than 30 letters containing a suspicious powder were mailed to Chase bank branches and federal banking regulators' offices in nine cities.

The Associated Press contributed to this report.

This is a developing story. Refresh page for updates.