Protests have broken out at a Mexico border town over potential coronavirus infections and deaths at the manufacturing plants of US companies Lear, Honeywell and Regal Beloit, it was reported on Thursday.

More than 80 people have tested positive, and 19 have died, in Ciudad Juarez across the border from El Paso, Texas.

Several Mexican workers for Lear Corporation, a Michigan car seat maker, have died from respiratory illness while one worker from the Juarez plant of Honeywell International Inc died after self-quarantining and receiving medical attention, the companies confirmed in statements to Reuters.

The deaths are among the concerns of Mexican workers protesting over deteriorating conditions at plants and factories operating during the coronavirus lockdowns.

Lear said it had ceased all employee-related activities by April 1 in Ciudad Juarez, a day after the Mexican government declared a health emergency that forced companies to cease non-essential operations.

"We are saddened that several employees at our Juarez City operations, who were receiving medical treatment at the same local government social security hospital in Juarez, have passed away, due to complications of respiratory illness," the company said in the statement.

As protests broke out at Honeywell on Thursday, the company closed the site for 48 hours to sanitize the area. They said in a statement to the company was "deeply saddened" to learn that one of its workers had died. Authorities had not confirmed if the cause of death was related to Covid-19.

"The products we manufacture at our sites are part of Mexico's critical infrastructure necessary to maintain essential activities and services including hospitals, health centres, laboratories, paramedics, and police and fire stations," Honeywell said.

Workers protested outside a manufacturing factory run by Regal Beloit, a Wisconsin-based company that produces electric motors for appliances, on Wednesday.

A protester who identified himself as a Regal Beloit employee said a colleague who had been working at the plant died on Wednesday night.

"There are infected workers and we are not being told," he told Reuters.