A Boston-area pet owner says her 16-year-old dog died after visiting Millennium Park in West Roxbury, believing exposure to blue-green algae (cyanobacteria) was the cause.

Both of her dogs became ill after the visit, but the older dog died two days later after developing severe symptoms. The Charles River Watershed Association said it is not aware of recent testing in that area, though cyanobacteria blooms have occurred on the river in past summers and can form quickly.

The MSPCA warns that toxic blue-green algae cannot be identified by appearance alone and can be dangerous to pets. While the owner is calling for stronger seasonal warnings, no official cause of the dog's death has been confirmed.

cbsnews.com