CONCORD - Police seized four local homes and millions of dollars worth of marijuana plants yesterday in what officials are calling the largest bust of its kind in the state's history.

Homes in affluent Chester, Derry and Londonderry neighborhoods were being used as labs to grow thousands of marijuana plants, police said.

The dealers, who grew the plants in the basements, installed their own utility meters to steal electricity to heat and grow the plants from seedlings. They stocked the homes with flammable chemicals and fertilizer that endangered the public, police said.

In all, 10 homes in nine New Hampshire towns were seized, six people were arrested and $24 million worth of marijuana was recovered, police said. Local and state police descended on the homes simultaneously yesterday in the culmination of an investigation that included the U.S. Attorney's Office, the state Attorney General, Immigration and Customs Enforcement and the Drug Enforcement Administration.

"This is a sophisticated criminal enterprise," Attorney General Kelly Ayotte said. "(This) group's houses were certainly a real danger to the public."

The two-month investigation began after police seized marijuana plants in Hooksett and Epsom. In Hooksett, an illegal connection to the power caused the residence to catch fire, and the operation was detected.

That led to yesterday's seizure of two Chester homes, one Derry home and one Londonderry home. Homes in Concord, Pembroke, Andover, Weare, Hopkinton and Canterbury were also seized because they were used to grow the plants. Police seized nearly $4 million worth of property.

"They're beautiful homes. They're very unsuspecting," said Col. Frederick Booth, director of the New Hampshire State Police.

Three of the six people arrested were found in the two Chester homes, but police wouldn't release their names or the names of the other three people taken into custody yesterday. They said the names and the charges would be made available today.

Booth said there are some connections among the homes, as many of the owners have the same or similar last names, but he wouldn't say if they were working together.

The four local homes seized ranged in value from $370,000 to $485,000. All were purchased during the summer, according to town assessing records.

In Chester, seven of the town's 11 full-time police officers, as well as firefighters because of the flammable nature of the operations, raided two homes yesterday. A total of 500 plants valued at $2 million were taken from 21 Penacook St., owned by Hai Bui. At 10 Partridge Lane, a home owned by Dung Nguyen, 1,000 plants valued at $4 million were taken.

Chester police Chief Alfred Wagner said it was apparent from the furnishings that people had been living regularly in the homes. The home on Partridge Lane even had family photographs hanging on the walls.

In Derry, 20 police officers entered 8 Gulf Road, the home owned by Hung Tran, to find more than 900 plants valued at $3.6 million. In Londonderry, 11 officers found 1,000 plants valued at $4 million at 7 Danbury Court, the home of Da Vav Ha. No one was home at either of those residences, police said.

Police are continuing the investigation, Booth said, and he asked for the public's help in identifying these labs. He said neighbors should be on the lookout for residents who move into large homes and don't bring much furniture or who keep their curtains drawn all day.