LISBON, Portugal (AP) — A police investigation into foreign trips for officials provided by a national energy company is making dents in Portugal's government.

The attorney general's office said Monday that the public prosecutor has classified three junior members of the center-left government as formal suspects in the probe into possible improper conduct in public office. That anti-corruption law carries a prison sentence of up to five years.

Prime Minister Antonio Costa said late Sunday he has accepted the resignations of those three officials, who were his secretaries of state for tax affairs, industry and business internationalization. They work under more senior government ministers.

The attorney general's office also said in its statement that a government special adviser, a chief of staff and a former chief of staff are also suspects.

The public prosecutor is questioning people who accepted trips from energy company Galp to watch Portugal's national soccer team play at last year's European Championship in France.

Galp was the Portuguese team's official sponsor and allegedly provided flights, accommodation and match tickets to the officials it invited. At the time, Galp was seeking to escape a new tax the government was introducing.

Investigators are assessing whether the trips amounted to influence-peddling and misconduct.