Justice advocacy groups announced that masks made by a company affiliated with a Quebec-based company are used in executions in the United States.

The non-profit organizations Worth Rises, based in the United States, and the Responsible Business Initiative for Justice said that the state of Alabama plans to execute inmate Kenneth Smith on Thursday by nitrogen hypoxia using a mask and tube typically used as a breathing device.

They added that the equipment is made by Allegro Industries, a subsidiary of Walter Surface Technologies based in Quebec, which is in turn partially owned by Toronto-based private equity firm Onex Corp.

Earlier this month, the United Nations Human Rights Office said this method of execution, which deprives the body of oxygen by forcing the prisoner to breathe only nitrogen, has not been tested and may cause severe pain.

The companies did not respond to requests for comment.

Correctional authorities have found it increasingly difficult to obtain the chemicals required for lethal injection due to pharmaceutical companies banning the use of their products for this purpose, prompting several states including Oklahoma and Mississippi to allow nitrogen gas as a means to execute death row inmates, although Thursday will be the first instance of this.