WASHINGTON (AP) — President Barack Obama has met with top national security officials to discuss the Boston Marathon investigation and the capture of the second suspect.

The White House says Obama convened the National Security Council midday Saturday for a 90-minute meeting in the White House Situation Room. Attorney General Eric Holder, FBI Director Robert Mueller and other officials briefed Obama on the investigation. Vice President Joe Biden joined by video conference.

The White House says Obama emphasized the need to keep gathering intelligence to answer lingering questions about the terrorist attack.

Still unknown is what motivated the two ethnic Chechen brothers that authorities say were behind Monday's deadly bombing that killed three. Authorities are also looking into whether they had help from others in the U.S. or abroad.