It happened around 8 p.m. in the 30000 block of Elizabeth Way.
Neighbors tell ABC7 News the explosion was so powerful, it knocked down shelving around their homes. Others add, the power was followed by pleas for help.
A HAZMAT crew from Alameda County Fire Department arrived on the scene, where officials found extensive damage to the home. Department officials say the house is likely uninhabitable.
There was no fire associated with the explosion, officials said.
There were five people inside the home during the explosion. Two men, a grandfather and his son, were injured in the explosion, according to the Fire Department.
Investigators say there were two containers of butane being handled. One canister was off-gassing and ignited inside the home.
#BREAKING Two people sent to the hospital after an explosion at a home in #UnionCity. One person taken to Kaiser in Fremont, the other to a burn center in San Jose. @AlamedaCoFire and @UnionCityPD_CA on-scene now. #abc7now pic.twitter.com/cCuJKyrC4O— Amanda del Castillo (@AmandaABC7) June 18, 2019
One victim was taken to Kaiser in Fremont, the other to a burn center in San Jose. Their conditions are unknown at this time.
The Alameda County Bomb Squad was brought in to safety dispose of the containers of butane.
The incident is under investigation.