AUSTIN, Texas — Austin police say the reward for information leading to the arrest of the person or persons responsible for three explosions that have killed two people and injured two others has grown by $50,000 and no totals $115,000.

Interim Police Chief Bryan Manley announced the reward boost Sunday as authorities pleaded for help.

Officials believe the bombings this month are related but Manley says investigators don't have a motive or “what the ideology is behind this.”

He says more than 500 officers, including federal agents, have conducted 236 interviews in following up 435 leads.

A package bomb exploded at an east Austin home on March 2, killing a 39-year-old man. Two package bombs in other parts of the city exploded last Monday, killing a 17-year-old boy, wounding his mother and injuring a 75-year-old woman.