A fourth youth has died in the explosion of a pipe bomb he and other teenagers were playing with Saturday in the garage at the home of a Brazilian diplomat, police said Sunday.

Police said the teenagers had been experimenting with explosives at the home of embassy counselor Vera Machado when the device blew up. It happened at about 3 a.m.Machado's 15-year-old son Gustavo was one of the dead, Montgomery County Police said.