GENEVA (Reuters) – The death toll from an accidental Nigerian air strike on a refugee camp in the town of Rann has risen to around 90 people, and could be as high as 170, Medecins Sans Frontieres (MSF) said in a statement on Friday.

Tuesday’s strike on the northeastern town in Borno state, which had Boko Haram militants as its target, has led to an investigation by the Nigerian Air Force (NAF). The inquiry’s report is due to be submitted no later than Feb. 2.

The aid group, also known as Doctors Without Borders, said the higher figure of 170 comes from reports from residents and community leaders.

“This figure needs to be confirmed,” said Bruno Jochum, MSF General Director, in the statement.

“The victims of this horrifying event deserve a transparent account of what happened and the circumstances in which this attack took place.”

Borno is the epicenter of Boko Haram’s seven-year-long attempt to create an Islamic caliphate in the northeast. The insurgency has killed more than 15,000 people since 2009 and forced some two million to flee their homes, many of whom have moved to camps for internally displaced people.

“A Nigerian airforce plane circled twice and dropped two bombs in the middle of the town of Rann, which hosts thousands of internally displaced people,” MSF said.

“At the time of the attack, an aid distribution was taking place.”

On Thursday, Human Rights Watch said the strike had destroyed 35 structures, and hit 100 meters from what appears to be a Nigerian military compound, raising questions about why precautions were not taken to avoid harming civilians.

(Reporting by Stephanie Nebehay in Geneva; Writing by Paul Carsten; editing by Ralph Boulton)