The New York state attorney general’s office has launched a criminal investigation into former US president Donald Trump’s company.

Attorney-General Letitia James has been investigating whether the Trump Organization falsely reported property values to secure loans and obtain economic and tax benefits.

The probe into whether the Trump Organisation inflated the values of some properties to obtain better loans and lowered their values to get property tax breaks is “no longer purely civil in nature”, office spokesman Fabien Levy said in a statement.

“We are now actively investigating the Trump Organisation in a criminal capacity, along with the Manhattan DA (district attorney),” he said.

It comes after a more than two-year investigation by Manhattan District Attorney Cyrus Vance into Mr Trump’s pre-presidency business dealings.

Property records show Mr Trump was loaned more than $US280 million ($A361 million) for four Manhattan buildings that prosecutors believe could “possibly reveal extensive and protracted criminal conduct at the Trump Organisation”.

The properties in question are Trump Tower on Fifth Avenue; a skyscraper at 40 Wall Street; a hotel and residential building on Columbus Circle near Central Park; and an apartment building on the Upper East Side.

The loans were made to Mr Trump by companies connected to New York City real estate investment trust, Ladder Capital Corp.

Mr Vance’s probe began after Mr Trump’s former lawyer and fixer Michael Cohen paid hush money to two women before the 2016 election about claimed sexual encounters with Mr Trump, which the former president denies.

That probe has accelerated since Mr Trump lost his bid for a second term to President Joe Biden.

The Trump Organisation could not immediately be reached for comment.

-with AAP