MEXICO CITY — Former President Álvaro Colom of Guatemala and his finance minister, who is now the chairman of Oxfam International, were arrested Tuesday in a graft case that is the latest chapter in the country’s sweeping attack on corruption.

The police arrested Mr. Colom and nine former members of his cabinet in early-morning raids after a long-running investigation into fraud involving a new bus system in Guatemala City.

Mr. Colom is the fourth former president of Guatemala to face corruption charges as a result of investigations led by an international panel of prosecutors trying to break up networks of corruption and end impunity.

Mr. Colom and his former finance minister, Juan Alberto Fuentes Knight, appeared at an initial court hearing in Guatemala City along with other former cabinet members, and were then placed in detention until a hearing scheduled for next week. Mr. Fuentes Knight, a well-regarded economist, has been the chairman of Oxfam International, a confederation of charitable organizations, since 2015.