Details suggested a pattern - that the items were packaged in manila envelopes, addressed to prominent Trump critics and carried U.S. postage stamps.
None of the devices have exploded.
The devices were thought to have been fashioned from bomb-making designs widely available on the internet, a federal law enforcement source told Reuters. Some were discovered in mail processing facilities.
The bombs have heightened tensions during the closing days of a highly contentious campaign ahead of the November 6 elections in which Democrats are battling to seize control of Congress now held by Trump's Republican Party.
Waters and Biden were each sent two packages. DOJ officials are set to brief reporters this afternoon. "It has gotten so bad and hateful that it is beyond description".
Brennan responded, tweeting that Trump should "Stop blaming others". The connection between this attack and hateful, violence-encouraging rhetoric is not hard to see.
Last February, the favorite actor of filmmaker Martin Scorsese, 75 years old, had even insulted publicly Donald Trump during the ceremony of the Tony awards of Broadway. Debbie Wasserman Schultz, the former chairwoman of the Democratic National Committee.
A 14th package was found on Friday at a post office outside San Francisco addressed to another wealthy contributor to the Democratic Party and liberal causes, Tom Steyer. Electrical wires leading out of the pipe led to an electric timer taped to the pipe, according to law enforcement officials speaking on condition of anonymity to discuss the investigation.
On Thursday morning, another device was discovered at the production offices of Robert De Niro in Tribeca.
"It struck him that they looked very much like a package he had seen Tuesday for" Robert De Niro's production company, Tribeca Productions, Miller said during a news conference with the Federal Bureau of Investigation and U.S. Postal Service. None detonated and no one has been hurt.
Authorities who have discovered the parcels around the country - in NY, outside Washington, D.C., in Florida and in Los Angeles - are sending them to the FBI Laboratory in Quantico, Va., for examination there.
Federal authorities have detained a person in connection with the mail-bomb scare that widened to 12 suspicious packages, a Justice Department official said Friday.
Meanwhile, actor Robert De Niro called on people to vote in the upcoming mid-term elections. They said investigators searching for more suspicious parcels had not found any during the previous eight hours.
Three days after the first explosive device found in the home NY financier and donor to democrat George Soros, no one has yet been arrested. Mr Soros has called Mr Trump's presidency "dangerous".
A police spokesman said the parcel "was similar to explosive packages that had been publicised".
So far, law enforcement agencies have detected eight explosives-laden suspicious packages sent to high-level current and former officials including Obama, former vice president Joe Biden and former secretary of state Hillary Clinton. They bore the return address of Florida Rep.
The two bombs sent to Brennan and Clapper were also addressed to CNN, and the bomb sent to Brennan actually made it into CNN's NY headquarters on Wednesday, sparking an evacuation of the building.
Photos on the van appear to feature President Donald Trump and Vice President Mike Pence, CNN, the Democratic donkey and the Republican elephant, and various American flags.
"Let's get along", he said at a Wisconsin rally Wednesday night. "Have you ever seen this?"
In response to the events, Trump decried political violence but also joked about moving to more polite speeches. "We must never allow political violence to take root in America".
Other Republican leaders said the same. As has been said before, words have consequences.
The FBI has appealed to members of the public to come forward with any information they may have as police study CCTV footage that may help identify couriers who dropped off the packages. Rep. Steve Scalise of Louisiana, the House majority whip, was struck in the hip and badly wounded.