By Mike Dougherty

PHILADELPHIA (CBS) — One of the largest tree and brush removal companies in the country pleaded guilty to hiring and re-hiring hundreds undocumented workers and will pay nearly $100 million to the feds.

Asplundh Tree Experts, based in Willow Grove, PA, have been contracted by utility companies like PECO, PSE&G, and others around the country to maintain the area near electric and gas lines.

US Attorney special assistant Josh Davison says the company’s management turned a blind eye for years while work was being done by illegal immigrants.

“Having those employees leave the company, and then turn around days and weeks later to be re-hired by the company, simply under different names,” said Davison.

Davison says a six-year audit revealed the company decentralized the hiring process so upper management could bury their heads in the sand while supervisors hired illegal workers through word of mouth referrals.

Asplundh has to fork over $95 million, the largest settlement ever in an immigration case.