Nearly half of Ontario's 77 electricity distributors have installed so-called "smart" meters manufactured by a U.S. company whose equipment has been linked to nine fires in Saskatchewan, Ontario's electricity regulator said Thursday.

Publicly owned Hydro One, Ontario's largest electricity distributor, doesn't use meters made by North Carolina-based Sensus, officials said.

But the Ontario Energy Board said it's still unclear how many of the 30 distributors who do use Sensus may have the Generation 3 smart meters that have raised safety concerns in other parts of Canada and the U.S.

Ten distributors have confirmed that they didn't use that particular model, and the remaining 20 are expected to report back to the OEB on Friday, said spokeswoman Karen Cormier.

"So far, we can say that we haven't heard of any safety issues," she said.

However, smart meters have been linked to 23 incidents reported to Ontario's Fire Marshal from 2011 to 2013.

"I can tell you 10 of those were smart meter failures attributed to internal faults, and 13 were small fires attributed to high-resistance heating," said spokeswoman Carol Gravelle.

No plan to remove meters

Ontario's governing Liberals say more than 4.78 million residential and small business customers in the province have a smart meter, which records consumption of electric energy in small intervals and can relay the information electronically to a power company. It eliminates the need to estimate bills when a meter reader can't do a check on site.

A spokeswoman for Energy Minister Bob Chiarelli said that, at this point, there is no plan to remove the smart meters because of fire concerns.

"We note that the investigation into the cause of the incidents is still in progress and that it has not yet been determined whether the issues originated from the meter itself versus an issue with the meter base or as a result of the installation process," Beckie Codd-Downey said in an email.

Sensus has said it conducted lab tests and site inspections to determine the cause of the "incidents" and the results so far point to "contributing external factors" such as holes in the meter boxes that allowed water in, or power surges.

"Safety is our number one priority and all Sensus meters go through rigorous testing and meet or exceed industry safety standards," company president Randy Bays said in a statement.

NDP urge quick action

But Ontario's New Democrats are pushing the government for answers, saying they've had a week to figure out how many Ontario homes may have the same equipment.

"It's imperative that the minister act quickly to find out whether we have these meters and have them removed immediately before somebody does get hurt or before somebody's home burns down," said NDP MPP Lisa Gretzky.

PowerStream, which serves several communities north of Toronto and in central Ontario, said it has installed more the 320,000 Sensus smart meters since 2007 and have used three different models.

But they've not had any fires, said spokesman Eric Sagen. So far, just one customer has called to ask about the meters.

SaskPower plans to remove all 105,000 of its smart meters and replace them with traditional units. Utilities in Philadelphia and Oregon have also reportedly decided to remove the Sensus meters after a number of devices overheated and some caught fire.

Safety concerns have also been raised in British Columbia, but the government says it's not aware of any problems with its smart meters, which are manufactured by Itron Inc., based in Washington state.