PLEASANTON — It started when a local woman answered an Instagram ad touting a free book about investing in the stock market, and it ended four months later, when she called police to report she’d been scammed out of $1 million, authorities said.

The plight of this Pleasanton woman is only the latest internet scam to affect a Tri-Valley resident. Police haven’t announced any arrests but say they’re still investigating how a woman was led to agree to pay $1 million to multiple couriers who went to her house close to a dozen times from June to August, occasionally calling in advance to confirm the pickups.

The woman reportedly believed she was going to learn from a professor who could predict stock market trends, and that she’d eventually join an investment project. She was told to pay the couriers foreign currency with the expectation of receiving returns in American dollars at a later date. Finally, in August, she realized she was being scammed, authorities said.

Police say the couriers sometimes used rideshare services to pickup cash from her Pleasanton home and that she believed she was talking to the stock market wizard’s assistant over social media.

In recent months, police have investigated similar incidents involving social media scams, including a Tri-Valley woman conned into sending “jet fuel” money to a person she believed was the country singer Morgan Wallen, and another Pleasanton woman who paid $200,000 to a courier after getting a popup ad that said her computer had been compromised, authorities said.