The latest in an increasingly worrisome string of vandalism affecting fiber lines in Northern California has prompted AT&T to offer up a $250,000 reward for information leading to an arrest of whomever is responsible.

Local media reports indicate the latest apparent acts of vandalism occurred on Monday night when fiber lines were accessed via a manhole and severed at two locations in Livermore, Calif., which is across the bay and about 40 miles inland from San Francisco.

The FBI is also looking into the matter. Earlier this summer, Special Agent Greg Wuthrich said, “Anyone who may have been in these areas during these times and saw anything either suspicious or related to normal telecommunications maintenance is urged to contact the FBI. The individuals may appear to be normal telecommunications maintenance workers or possess tools consistent with that job role.”

One incident was reported on June 9; an AT&T fiber-optic cable in Walnut Creek, Calif., was severed, prompting the carrier to offer up a $1,000 reward for information leading to a conviction.

The cable tampering led to a gap in wireless and landline service for area AT&T customers. AT&T technicians quickly repaired the cable, according to a spokesman, who also noted that 911 service was not affected, according to the Walnut Creek Patch.

The FBI recorded nine incidents between July 2014 and June 2015:

July 6, 2014, 9:44 p.m., near 7 th Street and Grayson Street in Berkeley.

Street and Grayson Street in Berkeley. July 6, 2014, 11:39 p.m., near Niles Canyon Boulevard and Mission Boulevard in Fremont.

July 7, 2014, 12:24 a.m., near Jones Road and Iron Horse Trail in Walnut Creek.

July 7, 2014, 12:51 a.m., near Niles Canyon Boulevard and Alameda Creek in Fremont.

July 7, 2014, 2:13 a.m., near Stockton Avenue and University Avenue in San Jose.

Feb. 24, 2015, 11:30 p.m., near Niles Canyon Boulevard and Mission Boulevard in Fremont.

Feb. 24, 2015, 11:30 p.m., near Niles Canyon Boulevard and Alameda Creek in Fremont.

June 8, 2015, 11:00 p.m., near Danville Boulevard and Rudgear Road in Alamo.

June 8, 2015, 11:40 p.m., near Overacker Avenue and Mowray Avenue in Fremont.