Top Democrat investigating Trump dies

US congressman Elijah Cummings, the Democratic chairman of a leading congressional committee investigating US President Donald Trump, has died at age 68.

Cummings was chair of the US House oversight and reform committee, a top investigative committee that along with two others is overseeing an impeachment inquiry into the Republican president.

"At approximately 2.45am on Thursday October 17, 2019, Congressman Elijah E Cummings (MD-07) passed away at John Hopkins Hospital due to complications concerning longstanding health challenges," his office said in a statement.

The statement said more information would be released later on Thursday.

The Maryland Democrat was first elected to office in 1996 and has served as chair of his committee since January after the Democrats gained control of the House of Representatives in 2018.

Along with the impeachment probe over Trump's handling of Ukraine, Cummings' committee has also demanded documents related to the president's personal finances as well as possible abuses in federal agencies in the Trump administration.

His panel has also been involved in fights with Trump's administration over subpoenas challenged by the president.

Cummings, the son of sharecroppers, was a trial lawyer before being elected to office to represent Baltimore and other parts of central Maryland, and has championed civil rights issues.

This past summer, Trump and Cummings were involved in a series of tweets and comments after the president said Baltimore was "rat and rodent infested".

Cummings was a graduate of Howard University where he earned a bachelor's degree in political science and the University of Maryland School of Law.

Cummings had been absent recently from Congress due to health concerns. He was previously treated for heart and knee issues, CBS News reported.