SACRAMENTO (AP) —  A flood of electronic alerts that was inundating California parole agents has dropped by half since The Associated Press first reported the problem two years ago.

The alerts are generated by satellite-linked ankle bracelets strapped to paroled sex offenders. They send alarms when offenders tamper with the devices, stray into areas where they’re not supposed to be or move too far away from home.

But the 1.5 million alerts sent by the bracelets in 2009-10, the first two years of the state’s electronic monitoring program, overwhelmed parole agents. Typical parole agents spent 44 percent of their workweek reviewing the computer-tracked movements of parolees and just 12 percent in the field, according to an internal California Department of Corrections and Rehabilitation report obtained by the AP at the time.

The number of alerts dropped to less than 744,000 for 2011-12, according to updated information obtained under a state Public Records Act request.

Several categories of alerts have diminished even more since July 2012, when the state went from two service providers to just one, Houston-based Satellite Tracking of People LLC. Changes in the programming of the GPS-linked bracelets in June 2011 and October 2012 also led to fluctuations in the number of alerts.

• In 2009-10, there were 1,520,591 alerts given off by electronic monitors in the following categories: 876 device tampers; 355,936 strap tampers; 17,017 exclusion zone alerts; 193,697 low batteries; 883,211 inclusion zone alerts; 69,854 message gaps.

• In 2011-12, there were 743,544 total alerts in the following categories: 536 device tampers; 92,174 strap tampers; 56,533 exclusion zone alerts; 86,451 low batteries; 408,658 inclusion zone alerts; 99,192 message gaps.

Among the recent changes:

• Satellite Tracking of People does not track device tamper alerts, and strap tamper alerts declined last year when the company let parole agents turn off the alarm while they investigated any initial alert showing that a parolee had damaged the strap securing the tracking device. The state also ended low battery alerts last fall in part because newer devices have extended battery life.

• The department decreased the time that ankle bracelets can be out of contact because of a blocked cellphone signal, which sharply increased the number of alerts due to what are known as message gaps.

• Exclusion zone alerts warn parole agents when a paroled sex offender approaches a prohibited area such as a school, park or playground. They can vary periodically when agents add or subtract zones, for instance if parolees are temporarily barred from an area where a county fair is underway.

• Inclusion zone alerts tell agents when paroled sex offenders leave certain areas, for instance when they leave their homes, pass beyond a 10-mile radius of their community or leave California. The number of alerts fluctuated dramatically in the last two years as the state made technical adjustments in the way the zones are monitored.