U.S. President Barack Obama said he ordered the “full resources” of the federal government to respond to the Boston bombings on Monday, and that he also called for increased security around the United States as necessary, CNN reported.

Obama, however, refrained from using the word “terror” when speaking of the explosions in Boston, which killed two people and wounded dozens of others.

“We still do not know who did this or why,” the president said, cautioning people against jumping to conclusions.

“But make no mistake, we will get to the bottom of this, and we will find out who did this, we’ll find out why they did this,” he added.

Any individuals or groups responsible for the “senseless” bombing, said Obama, will “feel the full weight of justice.”

“The American people will say a prayer for Boston tonight,” he said, according to CNN.

Despite Obama’s cautious words, federal investigators are classifying the bombings as a terror event. It is not clear if it’s from a domestic or foreign source, a federal law enforcement official with knowledge of the investigation told CNN.

Monday’s explosions struck near the finish line of the Boston Marathon. Reports of a third explosion later at the John F. Kennedy Presidential Library appeared to be false, as the library said there was an electrical fire that had been extinguished without causing any injuries.

According to CBS News, two bombs were inside trash cans near the viewing area close to the finish line. One unexploded device has been recovered, according to CBS.

Officials in other cities, including New York, tightened security as a result of the Boston blasts.