No arrests were made last week in the investigation of a Jan. 18 e-mail that threatened a "planned terrorist attack" against the University, Director of Public Safety Ed Callahan said. Callahan received the anonymous e-mail, sent from the Newton Free Library, about 11:30 a.m. The e-mail read that a terrorist attack would take place at the Heller School for Social Policy and Management.

After receiving the e-mail, Callahan informed the Waltham Police and Fire Departments who arrived on campus to evacuate the Heller School about noon and the science buildings about 1:30 p.m. as an added precaution, but no dangerous materials were found.

Callahan said the FBI is now the lead agency in the investigation. Gail Marcinkiewicz, a spokeswoman for the FBI's Boston field office, did not say Monday if any arrests have been made, nor did she disclose anything else regarding the case.

Waltham Police Chief Edward Drew said at a press conference the day of the threat that the department is working closely with the FBI on the case. No one at the police department Monday evening could provide any information about the case.

The University shut down its operations at 4:45 p.m. on Jan. 18, and advised everyone on campus to remain indoors while buildings were searched until 6:30 p.m.

Callahan said this is the first threat against the University warning of a "terrorist" attack, although six bomb threats have been made since 2003, including one last May that caused the suspension of final examinations in the Sachar Academic Complex. -Rachel Marder