In Maitland, Fla., residents of an upscale apartment building found a terrorism warning fastened to their doors. Tenants in Renton, Wash., received a similar warning in a letter from their landlord.

Yet most apartment dwellers in the United States received no direct notification of a recent FBI warning — sent to the agency's field offices — that Usama bin Laden's Al Qaeda terrorist network had discussed the possibility of renting apartments with the intention of blowing them up.

The warning, issued by the FBI in April and relayed more recently to some state and local law enforcement agencies, cautioned that the threat was unconfirmed and did not specify any target. A U.S. government official, speaking on condition of anonymity, said the information came from interviews with prisoners in Guantanamo Bay, Cuba.

FBI Agent Wendy Evans in Orlando, Fla., said Monday the warning was based on "uncorroborated chatter about explosives being left in an apartment."

"In an abundance of caution, we decided it was better (apartment managers) know than not know, so they would be aware of who they were renting to or in case of any suspicions they may have with a tenant," Evans said.

The Dallas-based real estate company Trammell Crow Residential said it received the FBI warning last week from the Real Estate Roundtable, a national trade association. The information was relayed to the more than 200 properties Trammell Crow owns nationwide, including Pebble Cove in Renton and the Alexan Club in Maitland.

"It (the warning) was very general, nonspecific, but we thought it was the right thing to do to pass it on," said Trammell Crow spokesman Tom Patterson.

The warning, one of many vague terrorism advisories issued since the Sept. 11 attacks, was handled differently from jurisdiction to jurisdiction.

In Richmond, Va., police were aware of the FBI advisory but — lacking specific guidance on steps to take — did not relay the information to apartment complexes, police spokeswoman Christie Collins said.

In Denver, police spokesman Sgt. Tony Lombard said officers were alerted in the event that they get calls about the warning or noticed anything suspicious.

"As far as notifying apartment owners, officers are encouraged to do that as they go and deal with apartment owners, but as far as a blanket notification, I don't see us doing that," Lombard said.

In Sacramento, Calif., sheriff's department spokesman Sgt. James Lewis said deputies were not contacting apartment managers.

"We get advisories on a regular basis," Lewis said. "They're reminders to us to stay on heightened alert."

In Los Angeles, the FBI field office reported a high volume of calls from renters complaining about suspicious neighbors. Callers were advised to report any suspicions to their property manager.

A police spokesman in Kansas City, Mo., Capt. Cy Ritter, said the department received the FBI advisory, but left it to the local media to spread the word to property managers.

There's been no public response, Ritter said. "We haven't received any calls at all," he said.

Harry Benjamin, vice president of Wirtz Realty Corp., which manages about 1,000 high-rise apartments in Chicago, said his company received no information about the warning from local or federal officials.

Benjamin said Wirtz was reminding staff to be vigilant and reviewing its security measures, making certain that vacant apartments were well-locked.