The bank robbers got away with an undisclosed amount of cash from the Bank of America when it opened Wednesday morning, but no one was injured in the robbery. No arrests had been made as of early Thursday.
A Los Angeles County sheriff's bomb squad disabled the device, but investigators said it wasn't an explosive.
The bank manager was snatched in front of her home Wednesday morning, said sheriff's Capt. Mike Parker. She arrived at her workplace wearing a device the men had strapped to her stomach.
"She was told that it was explosives and she was ordered to go into the bank and take out all the money," Parker said. "She did do that in fear for her life."
She ordered her fellow employees to remove the cash from the bank and it was thrown to the men who were waiting outside, authorities said. Parker would only say there was "a decent amount" of money at the bank and the manager did enter the safe.
The two men, who were armed with handguns and wore ski masks, took off in a two-door car and remain at large.
Parker said the woman remained inside the bank until a bomb squad arrived and removed the device from her body. The bomb squad later disabled the item with a robot. Nearby businesses were evacuated for a few hours as a precaution.
Investigators initially said they didn't believe the manager knew the robbers but they have conducted interviews to ensure she wasn't connected to the crime.
Authorities also haven't said how the bank manager was targeted by the robbers. Investigators are trying to determine if there were any video surveillance cameras that captured the incident.
Southern California has long been a target for bank robbers. Its most infamous heist was the televised shootout between Los Angeles police and two gunman wearing body armor in 1997. Both robbers were killed.
The area saw a three-decade low in bank robberies last year, tallying more than 280 across seven counties. In 1992, there were more than 2,600.
Using a bank manager to rob their own business is rare, authorities said, let alone strap a purported explosive device to an unwilling victim.
At least two movies have similarities to Wednesday's heist. "Bandits," a 2001 film starring Bruce Willis and Billy Bob Thornton, follows two inmates who escape from prison and start a bank robbery spree that includes kidnapping bank managers.
"30 Minutes or Less" from 2011 involves two ne'er-do-wells who force a pizza delivery driver to rob a bank while wearing a time bomb vest. The filmmakers said the movie wasn't based on the 2003 Pennsylvania collar-bomb case in which a pizza driver pizza delivery was killed when a metal bomb collar he was forced to wear while robbing a bank exploded.