With the Boston marathon-bombing suspect in a prison hospital, investigators are pushing forward both in the U.S. and abroad to piece together the myriad details of the plot that killed three people and injured scores of others.

FBI agents picked through a landfill near the University of Massachusetts Dartmouth where 19-year-old suspect Dzhokhar Tsarnaev attended classes. And U.S. officials said his mother had been added to a federal terrorism database months before the April 15 attack. His mother said it's all "lies."

Also, two college buddies of the suspect have been questioned, but a lawyer says they had nothing to do with the attacks. He says the two are being detained in a Boston jail for violating their student visas by not regularly attending classes.