BOSTON -- Thousands of Massachusetts households may be without power throughout the weekend, Gov. Deval Patrick said Friday after he declared a state of emergency in response to an ice storm that brought down trees and left about 350,000 residents without power.

Images Of Damage From Viewers | Photos: Ice Storm Downs Trees, Power Lines

Patrick said that the earliest that power would be restored was Monday and that residents should consider finding alternative shelter for the area.

"There is an extensive shelter system. It starts at the local level. Information on the shelters is available at the 211 line," Patrick said. "People who have lost their power should prepare for the amount of time it will take to restore the power. This is not going to take a couple of hours. It is going to be a couple of days."

Residents in Worcester were also cautioned not to remove trees because of the recent invasion of the Asian longhorned beetle. An area of the city has been quarantined because the beetles can bore dime-size holes in trees and eventually killing them.

"The best thing for managing the beetle is to move what can be moved to the side of the road and do nothing else," Patrick said.

Patrick said that the National Guard has been called, and crews are working to help clean up the storm damage.

"We have about 500 members of the National Guard being mobilized as we speak. They will help with road clearing, cutting limbs and debris," Massachusetts National Guard Maj. Gen. Joseph Carter said. "They will assist with any evacuations as necessary."

"We will be in touch with the federal government about a presidential declaration of emergency. That is triggered by the overall cost of the storm," Patrick said.

The governor said that he expects the storm damage to cost the state more than $7 million.

"All night my wife thought she was hearing fireworks, but it was trees snapping around us -- huge limbs down in backyard, trees blocking our dead-end street and neighbors who have electric meters ripped off their houses! Scary," one Worcester resident said.

State highway crews continue to remove downed trees, State Highway Commissioner Luisa Paiewonsky said.

"The primary problem was north and west of Boston. The Worcester area was particularly hard-hit," Paiewonsky said. "The primary focus we have is on the state highway system. There have been reports from local police departments, and we race out there as quick as possible."

Paiewonsky said that hundreds of crews were working to clear the roads.

"This would be a major storm, except with rain. So we probably have hundreds out right now," she said. "We will be continuing to work through the day. We need to be treating the roads because the temperatures will drop and we want to avoid freezing conditions as people head home in the afternoon."

Officials from several Bay State communities declared local emergencies in their communities.

"We want to minimize the folks that are out there. Some places, travel is going to be easier than others. We want people to use a little common sense. Crews are out there trying to get the roads cleared," said Peter Judge of the Massachusetts Emergency Management Agency.

In Marlborough, a Department of Public Works employee who was working during the ice storm has been reported missing. Kevin Connolly was last heard from at about 5 a.m. His vehicle was found in the DPW facility area.

Connolly, 50, has a medical condition and may appear disoriented, according to the mayor's office. He weighs 170 pounds, is about 5 foot 9 and has blond hair and a moustache.

"The town of Princeton lost power at about 10 p.m. We've been right at 32 degrees. The rain is heavy, and it is icing on trees," said Princeton Police Chief Charles Schmohl. "The three main roads that run through Princeton -- Route 140, 31, 62 -- are impassable due to the power lines down and the state of the roads."

Schmohl said that mutual aid has been called in, but he urged residents to stay off the roads.

"The trees are falling, breaking so fast that it is really dangerous for anyone to go out right now," he said.

Temperatures that lingered near the freezing mark caused ice and sleet to build up and bring down tree limbs. The ice coated power lines, causing many to snap.

The Massachusetts Bay Transportation Authority reported delays on some commuter rail lines as crews worked to clear downed tree limbs from the tracks. North of the Boston area, heavy rain in Lowell caused some street flooding and snarled the morning commute.

Due to power outages and hazardous driving conditions, the Registry of Motor vehicles closed branches in Leominster and Lowell for the day. In addition, road tests have been canceled at those locations as well as in Haverhill, Worcester, Nantucket and Lawrence.

In eastern and southeastern Massachusetts, the National Weather Service declared a flood warning, but there were few problems with ice because the temperatures were significantly higher.

Officials were forced to evacuate a flooded home in Southborough after a gas leak was reported.