The number of children found working illegally in the U.S. has risen by 44% over the last 10 months, the U.S. Labor Department said Wednesday as a group of bi-partisan lawmakers on Capitol Hill accused federal officials of not doing enough to protect unaccompanied migrant children from abuse.

More than 4,470 children were found working in violation of federal child labor laws between October of last year and July 20 of last week, the Labor Department said in a release that cited the conclusion of 765 child labor cases. More than 700 cases remain outstanding.

These outstanding investigations include the recent deaths of three 16-year-old boys in Mississippi, Missouri and Wisconsin.

The total cases resulted in more than $6.6 million in penalties to employers, a 87% rise from the same period in the previous fiscal year, the DOL said.