The 651 Serra St. building reopened Wednesday, Oct. 31, at 2:00 p.m after lab tests determined there was no biological hazard in the building.

A suspicious letter containing an unidentified substance was received at 651 Serra St. the morning of Tuesday, Oct. 30. As a precaution, the building was evacuated and remained closed while authorities conducted tests to identify the substance.

Tuesday's letter was the second such incident at 651 Serra St. in little over a week. On Monday, Oct. 22, the building was evacuated after an employee opened a piece of mail containing a suspicious substance and a threatening letter. Test results released Tuesday, Oct. 23, revealed that this substance also was not hazardous.

"Our community's health and safety is our paramount concern, and we will take every precaution necessary to ensure a safe workplace," President John Hennessy said Tuesday, Oct. 30. "I deeply appreciate the patience and dedication staff members have shown despite the difficult circumstances these situations present."

• Oct. 30 announcement about substance at 651 Serra
  
  
• Safety instructions for biological threats received by mail
  
  
• Guidelines for handling mail
  
  
• Bomb threat safety instructions
  
  
• Center for Disease Control: Facts about Anthrax
  
  
• Postal Service: Tips for opening mail
  
  
• A letter from Provost John Etchemendy following the Oct. 22 threat
  
  
• September 11 terrorist attacks: updates and resources