NEW DELHI - It was still dark outside when a spidery man in his underwear answered the knock at the factory door, releasing a wave of heat and gritty smoke from the noisy room behind him.

This, the man was told, was a power raid. The engineers storming past him were here to investigate electricity theft at this basement plastics mill. Please step aside.

The problem is rampant in India, but especially in New Delhi, a sprawling city of slums, factories, and politicians unaccustomed to paying for power. When companies from the private sector partnered with the government in 2002 to distribute the city's energy, more than half of electricity generated was stolen.

Since then, the energy companies have aggressively fought to stop the theft, a grueling battle that officials say they are slowly winning.

In a country facing massive power shortages, fighting power theft is an important way to make electricity distribution more reliable, officials say. Still, the shortfall is massive. In a nation of 1.2 billion, roughly 600 million people have no access to electricity at all, and those who do endure rolling blackouts that can last up to 12 hours. The demand is expected to grow by four to five times over the next 25 years, but the country's antiquated power grids are already overwhelmed.

India's energy deficit will be one of the most serious challenges facing Prime Minister Manmohan Singh as he begins his second term, and his administration is exploring nuclear, solar and wind power to address the gap.

This industrial block in west Delhi, home to a litter of stray puppies and a suspect plastics manufacturer, represents the front lines in the war on energy theft.

Vikrant Seth, the private sector enforcement official leading the raid, reviewed the plans in the pre-dawn darkness. He hoped this would be a big one - four police officers would accompany the team in case things turned violent, as they sometimes did.

A tired man with a thin mustache, Seth is one of the many people fighting block-by-block to clean up the system. It's an unenviable task. If Sisyphus had been Indian, his sentence might have been to unsnarl the boulder-sized knots of wire that hang from every electric pole.

Many Indians have a long-standing reluctance to pay for power, dating back to the era when the state controlled nearly the entire economy, including the energy sector, and securing a legal power connection could take a lifetime. Power companies across the country lose an average of 40 percent of the power generated, according to a 2007 government report.