Philadelphia Energy Solutions plans to shutter a key oil refinery after a mid-June explosion and fire destroyed most of the project.

Five employees were injured in the June 21 incident. No deaths were reported.

The blaze took more than 24 hours to extinguish. Experts say it would have cost more than $100 million to rebuild and were doubtful the company could have raised that amount. The cash-strapped PSE had filed under the bankruptcy laws last year and would have likely needed to file for it again, if it chose to rebuild.

In a tweet, Philadelphia Mayor Jim Kenney confirmed the largest refinery on the East Coast and one of South Philadelphia's largest employers would close, leaving about 1,000 employees and contractors out of a job. 

Representing the refinery workers, Ryan O'Callaghan, president of United Steelworkers Local 10-1, on Wednesday is meeting with the company's human resources director, Reuters reports. The union's contract requires a 60-day notice of layoffs.

PES produced 335,000 barrels a day -- a longtime concern for residents and environmentalists who say it is the city's biggest contributor to asthma and pollution.

At the same time, Reuters quoted O'Callaghan as saying that the closure could cost thousands more jobs from contractors and others who rely on the plant.

And the news service reported that closing the complex could crimp gasoline supplies in a busy and densely populated U.S. corridor.