"The packages were immediately identified during routine mail screening procedures as potential explosive devices and were appropriately handled as such", the Secret Service said.
A "pair of unattended packages" on Thursday evening prompted the evacuation of some areas of the Time Warner Center Mall, the location of CNN's studios in New York City.
A bomb was also sent to the NY offices of CNN, which resulted in the broadcaster evacuating the building live on air.
The package intended for Obama was intercepted in Washington, DC, and the one intended for Clinton was addressed to her in Westchester County, New York, on Tuesday.
The FBI in NY said they were aware of the suspected packages, and are aiding in the investigation.
Mr De Blasio also said there were "no other credible threats to New York City" after homemade explosives were shipped to the homes of Bill and Hillary Clinton and Barack Obama and other famous buildings such as the Time Warner building in New York and a Florida Democrat's Miami office.
Condemning the attempted attacks on Obama, Clinton and others, the White House said "these terrorising acts are despicable".
President Donald Trump bashed CNN for blaming it for "the current spate of Bombs" being mailed to top Democrats and prominent critics of his administration on Friday morning.
The New York Police Department's bomb squad believes package appeared to be an explosive device and the situation was under control, CNN reported.
USA to begin cutting aid to Central America
Mexican authorities insisted those on the bridge would have to file asylum claims one at a time in order to enter the country. One of the men fell off a truck in Mexico, and the other died trying to get onto a truck in Guatemala, authorities said.
Barack Obama, Hillary Clinton and liberal billionaire George Soros were among those targeted.
The first crude bomb to be discovered had been delivered Monday to the suburban NY compound of George Soros, a liberal billionaire and major contributor to Democratic causes.
The count jumped again on Friday, with suspicious packages addressed to Sen.
Federal investigators searched a massive mail sorting facility in Florida late Thursday, after determining that at least one of the pipe bombs was processed there.
Since Wednesday, a total of 12 packages containing explosive devices have been intercepted.
The package had actually been received in the general mailroom on Wednesday, according to a law enforcement official.
"We have seen an effort by the media in recent hours to use the sinister actions of one individual to score political points against me and the Republican Party", Trump said at a political rally in Charlotte, North Carolina.
"They were functional, but they didn't work, they didn't detonate because of a flaw in the design", Michael Balboni, former New York Homeland Security director, said on "America's Newsroom".