U.S. investigators say that the suspects in the Boston Marathon bombing were likely planning more attacks, as a cache of weapons was uncovered.

Boston’s Police Commissioner Ed Davis said in an interview with CBS on Sunday, local time, that police found an arsenal of homemade explosives left behind by suspects Tamerlan Tsarnaev and Dzhokhar Tsarnaev.

Police said that undetonated explosives were found at the scene of a gunfight between the brothers and police and inside an SUV they carjacked.

Investigators added that the suspects threw homemade bombs and grenades at the police when they were being chased in the stolen vehicle.