City officials and union leaders traded accusations over who is to blame for the power outage that shut down elevators, traffic lights and ATMs across much of Los Angeles (search) earlier this week.

The Los Angeles Department of Water and Power (search) said the outage, which affected approximately 2 million people, was caused when a utility crew incorrectly cut several control lines in the San Fernando Valley.

But a union official said Tuesday the mistake occurred during peak daytime hours because the city was "cutting corners" and reluctant to pay higher night wages.

Department of Water and Power (search) officials denied the allegation, and one city councilman questioned whether the mishap was done deliberately by employees to put pressure on the city during a contract dispute.

Ron Deaton, the utility's general manager, said it was an honest mistake. "That's all there is," he told officials at Tuesday's City Council meeting.

About 756,000 households and businesses with almost 2 million people from downtown Los Angeles to the San Fernando Valley lost power Monday for as long as 2 1/2 hours during lunchtime. There were no serious injuries or damage.

Workers were installing automated monitoring controls to provide the department with immediate information about the status of its system when the mistake was made.

Brian D'Arcy, an official with the union representing 8,200 utility workers, said technicians should have made the improvements at night, when power usage is lower and there is less potential for wide-scale shutdowns. He said city officials were reluctant to pay the higher wages required for night work.

"They're cutting corners," said D'Arcy, business manager for the International Brotherhood of Electrical Workers Local 18. "They shouldn't have done it in the middle of the day when people are coming back from lunch and turning their computers on."

Henry Martinez, the power department's chief operating officer, said at least nine other receiving stations and 34 smaller distribution hubs had been upgraded during normal working hours without similar mishaps.

The union claim came amid ongoing contract talks — a fact noted by Councilman Dennis Zine, who wondered whether the workers caused the shortage intentionally.

The City Council has yet to approve a proposal that would increase utility workers' pay between 16.25 percent and 30 percent over five years. D'Arcy said the union will hold a strike vote in the coming weeks.

"There's no question that water and power is in contract negotiations," Zine said at the City Council meeting. "Could this be interpreted as ... 'if we don't get this we're going to shut down the power of Los Angeles?'"

Power authorities intend to compile a report in the next two weeks explaining what happened. They also plan a longer investigation to determine what can be done to prevent any further accidents.