WINDSOR, ONT. -- A handful of Kingsville residents are still under an evacuation order, waiting until it’s safe to return home.

Crews are working to contain the underground gas leak that led the Town of Kingsville to declare a localized state of emergency, but the job to determine the source is proving difficult.

“If we don’t obviously the risk is an explosion, a serious impact to that block,” said Kingsville Mayor Nelson Santos.

The mayor says crews are working diligently to make sure that doesn’t happen.

On Tuesday, crews from a Sarnia based clean-up company attempted to pump water and mixed-fuel from below ground at the Arner Stop at the corner of County Roads 23 and 20 — but as they pumped it out, more fuel was pumped in.

“We’re creating an external sump pump to be able to pump out the original mix of the water and fuel to basically drain it up as best we can,” Nelson said of the approach used Wednesday.

It’s believed fuel is from an abandoned tank, possibly from a decade ago.

But as a precaution, crews are emptying all fuel cells on site before giving the all-clear.

According to Mayor Santos, a high pressure gas line is blocking excavation efforts, Enbridge gas is now assisting with the effort.

Meanwhile, four residents who live in neighbouring Essex are considered at risk and have made arrangements to live off-site.

Traffic is also being diverted at a wide berth to ensure the safety of everyone.

“It’s an inconvenience, obviously, but for the ultimate safety of everyone that will continue to be blocked off, we’ll continue to ask the public to avoid that intersection, find the alternate routes there,” Nelson said.

A statement from the Technical Standards and Safety Authority (TSSA) which has been on-site assisting with the issue says the cause of the leak is elusive, but emptying all the tanks will prevent any further leakage.

“TSSA issued orders for leak tests to be completed to determine the source of the leak. The initial tests were inconclusive. The area remains evacuated. A substantial amount of fuel has been removed from the sump pit in the crawl space of the building and remediation at the site continues,” the statement reads.

The fire department will make the final call when it’s safe for people to return home, Mayor Santos says residents can expect to wait at least another day.