The chairman of the charity Oxfam International, Juan Alberto Fuentes, has been arrested in Guatemala.
He was detained as part of an investigation into a corruption scandal dating back to his time as Guatemala's finance minister.
No charges have been brought so far.
While his arrest is not related to his role at Oxfam, it will heap further pressure on the charity, which is still reeling from revelations that its staff hired prostitutes in Haiti.
Oxfam International's executive director Winnie Byanyima said that Mr Fuentes had been "entirely open with his Oxfam board".
"He has assured us that he has co-operated fully with the investigation in the confidence he did not knowingly transgress rules or procedures," Ms Byanyima said.
It comes as Oxfam faces scrutiny over a scandal in Haiti in 2011, where senior aid workers - including the country director Roland Van Hauwermeiren - allegedly paid for sex. Some of the claims say the women may have been underage.
The scandal has forced the resignation of the organisation's deputy chief executive, Penny Lawrence, and shaken public confidence in both Oxfam and other charities.
Read more about the Haiti Oxfam scandal:
In Guatemala, Mr Fuentes is among 10 top former government officials arrested on Tuesday, including former President Álvaro Colom.
The ex-officials are being investigated in connection with a public bus system, which was developed during Mr Colom's government between 2008 and 2012.
No details have been given of the charges those arrested may face.
The investigation is being led by the International Commission against Impunity in Guatemala (CICIG). The commission is a United Nations body created in 2006 designed to strengthen the country's rule of law.
Ex-leaders in the spotlight
Apart from Mr Colom, those arrested are the former ministers of finance, interior, education, defence, employment, economy, health, culture and the environment.
Attorney General Thelma Aldana said that her office was investigating the purchase by Álvaro Colom's government of more than 3,000 buses in 2009.
Ms Aldana says that only 455 of the buses ever arrived in Guatemala.
Mr Colom is the second former president to be investigated over corruption by CICIG in the past months.
His successor in office, Otto Pérez Molina, who governed from 2012 to 2015, is due to stand trial for his alleged role in a huge corruption scheme involving Guatemala's customs service.
CICIG also said current President Jimmy Morales should be investigated because of alleged funding irregularities in his 2015 election campaign.
In response, President Morales said the CICIG's head had been interfering in Guatemala's domestic affairs and ordered his deportation, but the order was overturned by the country's highest court.