WASHINGTON >> Investigators searched coast-to-coast today for clues to the motives behind a mail bomb plot apparently aimed at critics of the president, analyzing the mechanics of the crude devices to reveal whether they were intended to detonate or simply sow fear two weeks before Election Day.

Law enforcement officials said the devices, containing timers and batteries, were not rigged like a booby-trapped package bomb that would explode upon opening. But the officials were still uncertain whether the devices were poorly designed or never intended to cause physical harm. A search of a postal database suggested at least some of packages may have been mailed from Florida, one official said.

The officials spoke on condition of anonymity because they were not authorized to discuss the ongoing investigation by name.

New details about the devices came as the four-day mail-bomb scare spread nationwide, drawing investigators from dozens of federal, state and local agencies in the effort to identify one or more perpetrators. In all, 10 packages had been discovered through today containing similar explosives. The would-be targets included former President Barack Obama, Hillary Clinton, former Vice President Joe Biden, actor Robert De Niro, CNN and others. The common thread between them was harsh criticism from President Donald Trump.

At a press conference today, officials in New York would not discuss possible motives, or details on how the packages found their way into the U.S. postal system. Nor would they say why none of the packages had detonated, but they stressed they were still treating them as “live devices.”

“As far as a hoax device, we’re not treating it that way,” said Police Commissioner James O’Neill.

Much was still unanswered about the devices, and authorities offered no clues about any suspects. Details suggested only a broad pattern — that the items were packaged in manila envelopes, addressed to prominent Trump critics and carried U.S. postage stamps. The devices were being examined by technicians at the FBI’s forensic lab in Quantico, Virginia.

The packages stoked nationwide tensions and fears as voters prepared to vote Nov. 6 to determine partisan control of Congress — a campaign both parties have described in perilous terms. Even with the sender still unknown, politicians from both parties used the moment to decry a toxic political climate and lay blame.

“A very big part of the Anger we see today in our society is caused by the purposely false and inaccurate reporting of the Mainstream Media that I refer to as Fake News,” Trump said on Twitter. “It has gotten so bad and hateful that it is beyond description. Mainstream Media must clean up its act, FAST!”

Former CIA Director John Brennan, the target of a package sent to CNN, fired back.

“Stop blaming others. Look in the mirror,” Brennan tweeted. “Your inflammatory rhetoric, insults, lies, & encouragement of physical violence are disgraceful. Clean up your act….try to act Presidential.”

At the briefing, authorities confirmed that at least some of the packages were distributed through the U.S. mail, and cautioned that there could be additional devices in the postal system. They said investigators searching for more suspicious parcels had not found any during the previous eight hours.