A business in Portstewart has been closed as part of the Health and Safety Executive investigations into gas safety concerns.
The Ice House Restaurant was closed in the town on Wednesday.
It is part of the HSENI's ongoing investigations following the deaths of two teenagers in Castlerock due to a suspected carbon monoxide leak.
Aaron Davidson and Neil McFerran, both 18, died in an apartment last Tuesday.
According to BBC NI's Natasha Sayee, there is no suggestion of carbon monoxide poisoning at the Portstewart premises.
On Wednesday in a statement, the HSENI said it has been working alongside gas safety companies to make safe a number of homes and premises in the Castlerock and Coleraine areas.
It said it had received almost 500 calls to its emergency helpline set up as part of the investigation.
Earlier on Wednesday, a gas fitter whose business is being investigatated over the deaths of the two teenagers expressed his sympathy to their families.
Calor Shop owner, George Brown, said he will co-operate with the authorities.
His shop in Coleraine was searched by police and the Health and Safety Executive (HSENI) investigating the suspected carbon monoxide leak.
The HSENI has advised anyone who has a gas appliance fitted by Mr Brown's business, the Calor Shop in Coleraine, to switch it off.
A solicitor released a statement on behalf of Mr Brown on Wednesday morning.
"Mr Brown would like to express his most sincere condolences to the Davidson and McFerran families following their tragic loss.
"Mr Brown fully supports the investigation being carried out by the authorities.
"He will help and co-operate to the fullest possible extent, and in any way possible, in order to assist the investigation into this tragedy."
"He has been in constant contact with the authorities since the tragic events have occurred.
The Calor Shop run by Mr Brown is an entirely separate legal entity to Calor Gas (NI) Limited.
The premises was searched by the authorities on Tuesday night.
Aaron and Neil, from Newtownabbey outside Belfast, had been spending time at the apartment awaiting their exam results when they were overcome by poisonous fumes last week.
A third teenager, Matthew McGaw, also 18, survived the leak.
The HSENI found that a liquefied petroleum gas appliance inside a flat at Tunnel Brae Court had not been working properly.