Thursday April 18, 2013 Happening Now - Fertilizer plant explosion kills at least 5, injures more than 150

A fertilizer plant has exploded in West, Texas killing as many as 15 people, and injuring more than 150. Firefighters are dead and missing. Apparently a fire broke out at the plant. When firefighters responded there was an explosion. Officials say they are investigating it as a crime scene, but that does not mean they have evidence it is suspicious. Nearly the entire town of West, TX has been damaged. Homes are flattened, businesses destroyed. Rescuers going door to door to search for injured. Secondary fires are being put out. One official described the damage as like a tornado where one home is destroyed, and another is left relatively unscathed. Casey Stegall and Dominic Di-Natale are reporting, and we'll add a couple of guests.

President Obama travels to Boston today to pay tribute to those killed and injured in the Boston terror attack. AT 11am there is a memorial service to honor the 3 killed, and more than 170 injured. It comes as investigators get new information on possible suspects. Police are using surveillance video and pictures to narrow the search. Apparently the FBI has distributed pictures of two potential suspects to police only. Rick Leventhal and Molly Line are reporting.

0840EDT -- Air Force One departs Joint Base Andrews to Boston. LIVE

0955EDT -- Air Force One arrives Boston. POOL LIVE

1100EDT -- POTUS makes remarks at "Healing Our City: An Interfaith Service." FLOTUS also attends. Cathedral of the Holy Cross, Boston, MA. LIVE

Lots of testimony today from the Hill on protecting the nation. Homeland Security Secretary Janet Napolitano, Attorney General Eric Holder and DNI head James Clapper testify at various hearings.

There's been an arrest in the ricin-laced letters sent to President Obama, a U.S. Senator, and a Mississippi justice department official. Paul Kevin Curtis was arrested yesterday evening in Corinth, Mississippi. Investigators do not believe there is a tie to the Boston attack.

A stinging defeat for gun control advocates yesterday as the Senate voted down expanded background checks and other measures to restrict guns. A visibly angry President Obama called it a "shameful day for Washington." He vows to continue to try and push for tighter gun control.

Labor Secretary nominee Thomas Perez is expected to face tough questions today at a Senate confirmation hearing.

Clint Henderson is the Executive Producer for “Happening Now” and an avid traveler. Follow his adventures on Twitter, ClintPHenderson, and Instagram, clintpage1.