(Bloomberg) - New York Attorney General Eric Schneiderman opened a fresh probe into one of Donald Trump's namesake operations - this time his charitable foundation - to determine whether the Republican presidential candidate is flouting state law.

The investigation into the Donald J. Trump Foundation, revealed by Schneiderman on Tuesday (Sept 13), throws up another legal concern for the billionaire ahead of the Nov 8 election.

Schneiderman's earlier fraud case against Trump University, in which he's accused of ripping off students with bogus real- estate seminars, is continuing along with two lawsuits by former students in San Diego.

"We have been concerned that the Trump Foundation may have engaged in some impropriety," Schneiderman said on CNN's "The Lead." "We have been looking into the Trump Foundation to make sure it's complying with the laws that govern charities in New York."

The probe gives Democratic candidate Hillary Clinton fresh ammunition as she seeks to get past questions over the propriety of her family's own foundation and portray Trump as untrustworthy. Schneiderman and Trump have a long history of exchanging harsh words, which may undercut his investigation.

"Attorney General Eric Schneiderman is a partisan hack who has turned a blind eye to the Clinton Foundation for years and has endorsed Hillary Clinton for President," Jason Miller, Trump's senior communications adviser, said in a statement. "This is nothing more than another left-wing hit job."