"Yesterday (Monday) the strike at Mai Tsebri occurred in the afternoon and killed 17 civilians working at the flour mill," said one of the humanitarian workers, citing witness accounts.
The aid worker said dozens of people were injured and 16 donkeys were killed in Mai Tsebri in north-western Tigray.
"A witness told me that the drones came and hovered a bit before dropping bombs. Then people panicked but after some minutes everyone heard huge shouting and they went to the scene to see that women and donkeys died."
The attack came after dozens of people were reported killed and many more injured in a drone strike on Friday on a camp, also in north-western Tigray, for people displaced by Ethiopia's brutal 14-month-old conflict.
It was not possible to independently verify the reports because access to Tigray is restricted and it remains under a communications blackout.
An Ethiopian government spokeswoman said on Tuesday she had no information on the alleged strikes.
Rebels from the Tigray People's Liberation Front (TPLF) say government forces are continuing to carry out air strikes despite them retreating to their Tigray stronghold in December.
Their withdrawal followed a government offensive that led to the recapture of a string of strategic towns, and had raised hopes of a possible opening towards a ceasefire.
On Friday, the government announced an amnesty for several senior TPLF figures and other high-profile opposition leaders in what it said was a bid to pave the way for national dialogue and "unity".
Fighting between forces loyal to Ethiopian Prime Minister Abiy Ahmed and the TPLF and their allies has killed thousands of people and forced several million from their homes since it erupted in November 2020.
Tigray itself is under what the UN calls a de facto blockade that is preventing life-saving food and medicine from reaching its six million people, including hundreds of thousands in famine-like conditions.
Monday's reported strike came on the same day that US President Joe Biden voiced concern about the continuing violence in a phone call with Mr Abiy.
Mr Biden expressed concern that "ongoing hostilities, including recent air strikes, continue to cause civilian casualties and suffering," according to a White House statement.
World Health Organisation chief Tedros Adhanom Ghebreyesus, himself a Tigrayan, also said on Twitter he was "deeply concerned about reports of another drone strike in #Tigray, resulting in injuries and death of too many civilians".
"I echo (UN) Secretary General Antonio Guterres' call for an end to the conflict in Ethiopia and for humanitarian aid to be urgently allowed in."
The aid workers who spoke to AFP on Tuesday also said the attack on the displaced persons camp in Dedebit had killed 59 people, with one reporting 138 wounded.
After that strike, aid agencies suspended their operations in the area, according to the UN's emergency response agency OCHA.