Ateeq Baig, 2-2, has been murdered in the wreck from Daman-e-Koh, north of Islamabad, on 7 April.
Later, the Interior Ministry had placed the U.S. diplomat's name on a blacklist, prohibiting him to leave the country without prior permission.
The Kohsar police arrested Syed Taimoor Iqbal from the parking area of the district and sessions court Islamabad as he had allegedly threatened and assaulted the police officials besides assisting a USA diplomat, escape from police custody after a fatal traffic accident.
The court during the hearing also remarked that the United States diplomat did not have absolute immunity in the country.
Moreover, a security official of Colonel Hall has been arrested on the orders of AIG Islamabad for obstructing a police official from performing his duty, a source said.
The U.S. embassy and Pakistan's Foreign Office declined to comment.
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Hall was stopped at the immigration counter and informed that he could not leave the country, the official said.
The US embassy has also reportedly handed over passport of the diplomat to FIA immigration officials, who are awaiting orders from the top authorities for further action.
The US representatives waited for four hours at the Pakistani airbase but the FIA officials did not allow Hall to leave the country as his name was put on the blacklist by the Ministry of Interior.
"For the privacy and security of those involved, we can not disclose the diplomat's current location", the State Department spokesperson said. "We do not want to comment on that", the spokesman told Anadolu Agency.
The United States has significantly contributed Pakistan more than 33 billion dollars in support during the previous 15 decades, and they have granted us nothing but lies deceit, believing about our leaders as fools. Six weeks ago, the State Department threatened to impose a travel restriction on Pakistan's Washington diplomatic corps if the harassment did not end by Friday.
In what the Times described as retaliation, Pakistan placed travel restrictions on USA diplomats based in the country in a sign of worsening relations between the two countries.
U.S. authorities have previously said he can not be detained or attempted because he's got diplomatic immunity.