It might have sounded like a bomb. 

And, the way that it was placed on the inside of a protective sand barrier near the Union Pacific Railroad tracks as they crossed Airport Way near Northgate Drive, it certainly looked like it might have been a bomb. 

But when explosive ordinance experts opened up the black plastic bag Tuesday evening – after closing the busy stretch of roadway for hours and taking every precaution necessary to ensure that the safety of the first responders and the homeowners nearby – they discovered an unlikely pairing. 

A cell phone attached to a cord and a smoke detector with a dying battery. 

According to San Joaquin County Sherriff’s Department Public Information Officer Les Garcia, the smoke detector was determined to be responsible for emitting the “beeping” sound that drew a law enforcement response from Lathrop and Manteca and brought in experts from the Federal Bureau of Investigation. 

The San Joaquin County Metropolitan bomb squad – a multi-jurisdictional entity – used a mobile robot to get a closer look and stationed responding personnel behind units as a precautionary safety measure. The four-hour ordeal diverted traffic and held up four freight trains that use the tracks to transport goods throughout the Central Valley. 

Manteca Fire Department crews also instituted a voluntary evacuation for homes that could have been within a blast area – notifying as many as 20-homeowners along Gianna Lane that they might be in danger.

Garcia said that no additional information is being released at this time. No arrests had been made as of Wednesday night.