US impeachment investigators said on Monday that they could present their report of presidential wrongdoing as early as next week but do not rule out calling new witnesses in the case against Donald Trump.

The three panels heading the probe have been preparing a file to deliver to the committee that will consider whether to draft articles of impeachment against the president.

House Intelligence Committee Chairman Adam Schiff told colleagues in a letter, “It will be sent to the Judiciary Committee soon after Congress returns from the Thanksgiving recess, beginning next Tuesday”.

“The evidence of wrongdoing and misconduct by the president that we have gathered to date is clear and hardly in dispute,” said Schiff.

Schiff presided over two weeks of dramatic public hearings that he said uncovered a “massive amount of evidence in short order,” despite efforts to obstruct the investigation by Trump and his administration.

Last week, David Holmes, a staffer from the US Embassy in Ukraine, who also testified described a conversation he overheard between Trump and US Ambassador to the European Union Gordon Sondland, which occurred on July 26, a day after a Trump-Zelensky phone call that triggered an anonymous whistleblower complaint and the impeachment inquiry.

Initially, President Trump described the impeachment probe against him as “witch hunt”, saying he was “too busy” to watch it.

In October, President Trump opposed impeachment enquiry, saying that there should be no public hearings during the House of Representatives’ impeachment enquiry against him, and directed White House Chief of Staff Mick Mulvaney not to appear before the committees investigating Trump’s phone call to Ukraine.

After almost a month of calling for greater transparency in the enquiry, the White House changed its strategy this week by prohibiting several of its officials from even testifying behind closed doors before the lower house committees.

Late September, the impeachment inquiry, which House Speaker Nancy Pelosi initiated over a complaint by an anonymous whistleblower, is looking into White House’s alleged efforts to withhold military aid to have Ukraine investigate a Trump’s political rival, Joe Biden.

(With inputs from agency)