President Muhammadu Buhari approved her suspension on May 5 after a reported cold war between her and Rotimi Amaechi, minister of transportation.
She was initially accused of failing to remit the operating surplus of NPA to the consolidated revenue fund (CFR) — an allegation she denied.
Amaechi has inaugurated an 11-member investigative panel to probe NPA over all contracts awarded since 2016 when she became managing director.
Sirleaf, who served from 2006 to 2018 as the first female president of the West African country, said the rule of law, fair and equal treatment should be observed as investigations is carried on.
“I am disheartened to hear about the suspension of Nigerian Ports Authority MD @hadizabalausman, who I have known to be an accomplished leader and dedicated public servant,” the tweet read.
“I urge adherence to the rule of law and fair and equal treatment as the situation evolves.”
Buhari approved the appointment of Mohammed Koko, the executive director (finance and admin), as acting MD.
The probe panel does not have any deadline for the submission of its report.