LOS ANGELES --- Two Los Angeles traffic engineers admitted to hacking into a computer system that controls traffic lights before a job action related to contract negotiations with the city, according to prosecutors.

Gabriel Murillo and Kartik Patel, who worked with the city's Automated Traffic Surveillance Center, each pleaded guilty to a single felony count of illegally accessing a city computer connected to the center, the Los Angeles Times reported.

The hacking occurred hours before a job action in August 2006 by members of the Engineers and Architects Assn. The group represents the engineers who run and maintain the city's traffic center.

It took four days to get the traffic control system fully operational after the hacking, revealing the vulnerability of L.A.'s complex system, the Times reported.

The security breach, reported on Aug. 21, 2006 between 9:10 and 9:30 p.m., involved sending computer commands that disconnected four signal control boxes at critical intersections: Sky Way and World Way at the airport; Coldwater Canyon Avenue and Riverside Drive in the San Fernando Valley; Alvarado Street and Glendale Boulevard at Berkeley Avenue in Echo Park; and 1st and Alameda streets downtown.

Prosecutors argued that the traffic engineers chose intersections they knew would cause significant backups because they were close to freeways and major destinations. They said the red lights would be extremely long on the most congested approaches to the intersections, causing gridlock for several days.

Under the plea deal, sentencing will be delayed one year, said Jane Robison, spokeswoman for the Los Angeles County district attorney's office. The two must pay full restitution, serve 120 days in jail or complete 240 hours of work with Caltrans or other community service, and must have their computers at home and work monitored, the Times reported.

Defense attorney James Blatt, the lawyer for Murillo, said his client had been an exceptional employee and that the matter should have been handled administratively. He noted that despite pleading guilty to a felony, both men would be sentenced to one misdemeanor count and that after a brief period of probation, both sides would dismiss the count and expunge their criminal records, the L.A. Times reported.

"This was an emotional collective-bargaining strike situation," Blatt told the L.A. Times. "This should have been handled administratively."