(Reuters) - The U.S. Department of Labor (DOL) is investigating Hellofresh over allegations that migrant children were working at the meal-kit maker's cooking and packaging facility in Illinois as recently as this summer, ABC News reported on Friday evening.

The department is also investigating if Midway Staffing, an agency hiring employees to work at the facility, violated child labour rules, the report said.

Shares in the German firm fell 7% on Monday morning with traders pointing to the report.

A Hellofresh spokesperson told Reuters that both Midway and Factor 75, Hellofresh's U.S. and Canada subsidiary, were part of the investigation. "To be clear, neither Hellofresh nor Factor have ever hired or employed the alleged underage workers. That has always been through Midway Staffing," she said.

"As soon as we learned of these allegations, we immediately terminated the relationship," the company said in a statement.

"We have zero tolerance for any form of child labour, and we have taken action to ensure no minors perform work in or have access to our facilities," it added.

The spokesperson for the company couldn't comment on when exactly the contract was terminated due to the ongoing investigation.

Midway told Reuters it was cooperating with the DOL in its ongoing investigation.

"Midway Staffing has provided the Department with all payroll, time and personnel data the Department has requested related to workers it placed at certain Illinois facilities operated by Hellofresh," it said. 

Midway also denied that its actions or practices contributed to or caused any alleged child labor violations and added it refused to knowingly hire anyone who is not at least 18 years of age.

The DOL did not respond to requests for comment.