Technical experts will be heading to a small community in southwestern Ontario to find the source of a recurring gas leak suspected of causing an explosion last week, officials said Wednesday.

Twenty people required medical attention and a building was levelled after the blast that took place in Wheatley, Ont., last Thursday. One person remains in hospital. 

The area where the explosion took place was being evacuated due to a suspected gas leak for the third time in recent months when the blast occurred. 

The mayor of Chatham-Kent, which includes Wheatley, said the situation had to be addressed. 

"It's essential that we find and remediate the source of this gas because if we don't, the citizens of Wheatley will be living in fear of when's the next leak going to happen," Darrin Canniff told reporters. 

Canniff had called last week for the provincial government to help find the source of the leak because local officials didn't have the expertise or authority to do so.

Chatham-Kent's chief administrative officer said Wednesday that technical experts from the province would be arriving in the community in the next few days to investigate a hydrogen sulphide leak thought to be behind the blast. 

Don Shropshire said the leak could be coming from an abandoned gas well or from an unknown underground source. 

"We don't know whether someone's going to identify the source on the first attempt, or whether that's going to take several attempts," he said. 

"We need to not only get control of the initial emergency but also to try and find the source of the gas, take steps to mitigate it so we're not going to be dealing with this every several weeks."

The explosion at a privately owned building in downtown Wheatley was close to a location where hydrogen sulphide gas was first discovered in June, prompting an evacuation order and the declaration of a state of emergency.

In July, the municipality declared a second state of emergency after confirming hydrogen sulphide was once again present in the building that was levelled in Thursday's blast. 

Ontario's solicitor general said on Friday that the province had launched an investigation and would be working closely with the municipality.

Chatham-Kent's fire chief said crews were methodically removing debris from the blast site to allow provincial experts to get to the suspected source of the leak. Chris Case noted that there's no gas currently detected at the site. 

Officials said there was no timeline established for when residents can return to the two-block area around the blast site, or when the source of the leak will be found. 

More than 120 households sought aid following the explosion and Shropshire said Wheatley is currently providing emergency shelter for 27 people. Others are being housed in hotels across Chatham-Kent and Leamington, Ont. 

The cost of the damage from the explosion has yet to be determined. 

This report by The Canadian Press was first published Sept. 1, 2021. 

Elena De Luigi, The Canadian Press