US house Democrats sought to investigate about firings of top Department of Homeland Security officials, saying they were concerned the dismissals were prompted by the officials' refusal to break the law.

 Iran Press/America: "The president may have removed DHS officials because they refused his demands to violate federal immigration law and judicial orders," three US Democrats Elijah Cummings, Bennie Thompson and Jerrold Nadler, who head the House of Representatives Oversight, Homeland Security and Judiciary committees concerned, Reuters reported.

The chairmen said they were particularly interested in documents relating to recent moves by President Donald Trump and Stephen Miller, a former congressional aide who has become a top presidential adviser on immigration, to purge DHS of senior leaders' who 'reportedly refused orders to violate the law.

The committee leaders’ move followed a declaration that it was refusing a request from the Oversight Committee for Miller to testify before the panel.

In a letter to the committee on Wednesday, the White House said Miller would not testify about administration immigration initiatives, including Trump’s policy of separating migrant children from their parents and his threat to send immigrants in the country illegally to so-called sanctuary cities.

A video appears to show Arizona Southwest Key staffers dragged, pushed and pulled migrant children.

"In accordance with longstanding precedent, we respectfully decline the invitation to make Mr. Miller available for testimony before the committee," the White House counsel said in the letter, which was provided to Reuters on Thursday.

The Republican president is pushing back against legal requests from Democratic-led House committees, which are conducting wide-ranging investigations of Trump and his administration, including his tax returns, White House security clearances and possible obstruction of justice by Trump.

Cummings, whose committee has launched multiple investigations into Trump administration and White House policies, accused Trump on Wednesday of an 'unprecedented, and growing pattern of obstruction' after he ordered federal employees not to comply with congressional investigations.101/209/213

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