Security tight in Brussels following bombing attacks

People around the world mourning the 31 killed in Tuesday's terror attacks in Brussels.

The terror alert there remains at its highest level... Meaning authorities believe there's a risk for an imminent attack.

This, as the search for suspects continues.

Security tight in the Belgian capital following Tuesday's attacks.

Authorities say several people possibly connected to the deadly blasts are on the run.

One of them is the man in a light jacket seen here with two suicide bombers at the airport.

The suspect in the middle of the surveillance photo identified as 29 year old Ibrahim el Bakraoui, a native of Belgium.

His brother, 27-year-old Khalid, blew himself up in the subway station attack.

Prosecutor Frederic Van Leeuw said, "The two terrorists who died had substantial criminal records unrelated to terrorism."

Belgium holding three days of national mourning for the victims.

Crowds gathering at the Place de la Bourse, leaving behind flowers and other mementos.

Vice president Biden and his wife among those paying their respects, visiting the Belgian embassy in Washington and signing a condolence book.

The vice president telling the Belgian ambassador those responsible will be defeated.

"We are prepared to provide any and all information, capability, technology. Anything we have that can be value added to their fight," Biden said.

ISIS taking responsibility for the deadly blasts.

President Obama says going after the terror organization is his top priority.

"I've got two young daughters who are growing up a little too fast. And I want them to have the freedom to move and to travel the world without the possibility that they'd be killed," Obama said.

Officials here say more explosives and bomb-making materials were found at the house the suspects left on their way to the airport.

A taxi driver who took the three to the airport tipped off authorities.

Secretary of state John Kerry will travel to Brussels Friday to express the condolences of the U.S.