(AP Photo/The Record, Craig Sanders)

LINDEN, Calif. - More than 300 human bones have been unearthed from a well in rural California, where a convicted serial killer said there might be 10 or more victims from a killing rampage in the 1980s and 1990s. Rain could slow the search as it was expected to continue Monday.

The remains were found in just two days of searching an abandoned cattle ranch, San Joaquin County sheriff's spokesman Deputy Les Garcia said in a statement.

"We are bringing the dirt and debris up using excavators and we're searching piles," Garcia said. "If it's raining, we will wait."

The remains were found with the help of a map prepared by death row inmate Wesley Shermantine. He and childhood friend Loren Herzog became known as the "Speed Freak Killers" for a methamphetamine-fueled killing spree that claimed as many as 15 victims from the 1980s until their arrests in 1999.

Shermantine was convicted of four murders and sentenced to death. Herzog was convicted of three murders and sentenced to 77 years to life in prison, though that was reduced to 14 years. An appeals court tossed his first-degree murder convictions after ruling his confession was illegally obtained.

Herzog was paroled in 2010 to a trailer outside the High Desert State Prison. He committed suicide outside that trailer last month after a bounty hunter, Leonard Padilla, told him Shermantine was disclosing the location of the well along with two other locations.

Crews are expected to be searching the ranch for several days, at what Garcia has said would be a "slow and tedious" pace. The property was once owned by Shermantine's family.