Riddle urged the mayors, gathered for their National Housing Forum, to "reach out to your communities and reassure them of city security and safety."

Boston mayor Thomas Menino, newly appointed Conference president, responded by explaining that Boston had already taken the lead and drafted an evacuation plan for all high-density buildings after the Sept. 11 attacks.

On May 16, NMHC vice president of property management Jay Harris circulated a memo to the combined membership stating that the groups' "Joint Legislative Program has been advised that the FBI's Counter-Terrorism Division is directing field offices to pass general threat information to state and local law enforcement agencies. [This information would] facilitate their coordination with appropriate public housing authorities, property management companies and apartment management personnel."

The memo went on to characterize the "general, non-specific threat: There are indications that discussions were held about the possibility of renting apartment units in various areas of the United States and rigging them with explosives. The FBI has no information indicating that this subject advanced beyond the discussion stage."

Nevertheless, the NMHC is clearly taking the threat seriously. In an interview following her plea, riddle told GlobeSt.com that the organization has also beefed up its post-Sept. 11 security program and has outlined an additional 41 measures that apartment owners are wise to embrace. All of the measures are now available on the association's website (www.nmhc.org) and are being made available to the entire industry beyond NMHC membership.

The measures include such recommendations as keeping non-public areas--especially equipment and storage areas--off limits to all but identified employees; monitoring vacant units on a regular basis; and inventorying industrial-grade chemical supplies. The Council also urges all building personnel to report all suspicious activity to the Joint Terrorism Task Force representative at their local FBI field office.

While putting membership on increased alert, the May 16 memo from Harris urged them to avoid panic in its treatment of residents. "Companies are advised to remember the Fair Housing Act prohibitions on discrimination," he wrote. Also, membership was cautioned to respect "limitations on sharing non-public resident and applicant data under state and federal resident privacy laws."