NEWPORT, R.I. (AP) — National Grid began the painstaking process Tuesday of going door-to-door to restore natural gas service to about 7,000 Rhode Island customers who were without heat on a day when temperatures weren't expected to rise above freezing.

The effort in Newport and Middletown could take a week or more, Tim Horan, president of the utility in Rhode Island, said at a morning news conference with Gov. Gina Raimondo. The pair held a second news conference in the evening, during which Horan suffered a medical emergency at the podium and was taken to a hospital. National Grid spokesman Ted Kresse tweeted about two hours after the incident that Horan is doing well and should be released from the hospital.

The utility suspended service Monday following a potentially dangerous loss of pressure caused by a supplier's faulty valve. In such cases, there can be explosions as pressure is restored, but National Grid shut down service out of an "abundance of caution."

An overpressurization issue was blamed for multiple explosions, fires and one death in the Lawrence, Mass., area in the fall. Horan said the current situation was different, and that "the integrity of our system is safe and intact."

"We know this situation has created a huge challenge for everyone," he said.

Although temperatures are expected to rise to near 50 degrees later this week, Raimondo is urging residents to find alternate accommodations. She declared a state of emergency and deployed the National Guard to get people without heat to somewhere warm. She urged people to call 211 to be picked up.

National Grid said it would reimburse affected customers for hotel stays.

Elizabeth Brooks, a retiree from Newport, knew something was wrong Monday morning when she turned up the heat and nothing happened. Still, she and her husband and their cat are staying put.

She said she never felt in danger. "It's just annoying," she said. "We're cold. The house is quite chilly. But we're not going anywhere. We have four fireplaces and an electric blanket for night, so we're all set."

National Grid technicians are going door-to-door to restore gas service. They will be accompanied by locksmiths and police officers in case they need to get into an unoccupied home.

Several warming centers were set up in the area and National Grid set up a customer service center at a local hotel that still had heat.

Newport Public Schools and Salve Regina University canceled classes Tuesday although the university said the campus would remain open.

Newport's schoolchildren will likely have the week off, Mayor Jamie Bova said, because none of the schools have heat. The police and fire departments were without heat, but the local hospital does have heat, she said.

The lack of heat also forced officials to close Newport's courthouse.

A Middletown animal shelter, the Potter League for Animals, offered to take in pets of people unable to bring them to shelters or hotels.