Some Shell gas stations across Ontario are sitting empty for a second day because maintenance work at the company's Sarnia oil refinery took a week longer than expected.

The gas drought, which has affected Shell stations and even some smaller fueling stops from Toronto to London, began Tuesday.

Several gas stations, including one near Highway 401 and McCowan Road, ran out of gas as early as 10 a.m. on Tuesday leaving many drivers frustrated and confused.

A spokesperson from Shell Canada told CTV Toronto that normally, the company turns to the open market for gas. However, they are having trouble buying gas from fuel markets in the province and the northeast United States.

"We usually are able to tap into the southern Ontario supply market. But when we went looking into the market place there really wasn't a whole lot available. It was extremely tight," Jeff Gabert said.

Gabert added that an upgrade and closures at two other refineries may also be contributing to the gas drought.

He told The Canadian Press that maintenance delays are not unheard of, but that the tight supply in fuel markets is unusual.

With files from The Canadian Press and a report from CTV's Collin D'Mello