Uranium hexafluoride leaked at an Illinois plant on Sunday.

A uranium hexafluoride plant operated by Honeywell International Inc. at Illinois is undergoing investigation for the incident of chemical leak on Sunday, reported Reuters.

Honeywell's company spokesman, Peter Dalpe confirmed the leak incident on Sunday evening at its Metropolis, Illinois plant. According to Dalpe, there were no injuries and no one was endangered by the leak. He also added that there's no evidence that shows the chemical leak escaped the compounds of the building.

A US Nuclear Regulatory Commission (NRC) inspector started investigating on the plant Tuesday, reported NRC spokesman Roger Hannah.

"At this point we're still in a fact-finding mode," Hannah said. "We haven't come to any conclusions about whether processes weren't followed." The investigation could take a few days to a week.

It was not yet clear how much of the uranium chemical has been released.

Dalpe also ensured that all the plant workers executed all the emergency procedures and plant safety systems were performed as designed. An example of this system is water mitigation system sprayed into the air after the leak to eradicate and contain the chemical.

The three year contract of about 135 members of United Steelworkers Local 7-669 have ended starting August and were have been locked out of the plant since then.

John Smith, spokesman of USW Local 7-669, said he could not say what could have been different in the leakage situation had the union's workers got back to the Illinois plant. "But I definitely know that our members have a lot more experience than the people running the plant right now," Smith said.

Uranium hexafluoride is a radioactive compound that when released in air can be hazardous and toxic.

Honeywell's Illinois plant is the only facility in the U.S. that converts uranium oxide into uranium hexafluoride or UF6. It is then enriched to be used as fuel in nuclear power plants.