(KPIX 5) — Authorities have tracked the mailing address of package bombs sent to two Bay Area families, hurting two people when the devices exploded.

Law enforcement sources told KPIX 5 the mail bombs listed the sender as a fake jewelry store from a fake address in Palo Alto.

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The sources said the bombs were triggered when the packages were opened past three inches.

Friday, one of those packages was delivered to a police officer’s home on Bay Farm Island in Alameda, injuring the officer’s wife after she opened it.

Last month, a similar bomb was sent to a home in East Palo Alto where it exploded and injured a father.

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Investigators worked to reconstruct the most recent package to find the mailing label. They believe both packages were made by the same person.

“These things are dissected very, very carefully,” said KPIX 5 Security Analyst Jeff Harp. “They look for all the pieces and parts and they’ll do DNA analysis, they’ll do fingerprinting analysis, they will construct as much of that back together as they can. They’ll look at what the parts are made from.”

Investigators are reviewing post office surveillance video to see who dropped the packages off.

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They’re also looking into the possibility the officer was targeted as a form of payback; last summer the officer testified in a case involving Tongan gang members.