A European Union observation mission said Tuesday that Colombia’s presidential vote count has been transparent and efficient, countering President Gustavo Petro’s repeated claims of irregularities after results did not favor his preferred successor.

The independent mission deployed about 150 observers for Sunday’s runoff election, which showed conservative outsider Abelardo de la Espriella leading by roughly 1 percentage point, or nearly 251,000 votes, with nearly all ballots counted. The mission also monitored May’s first-round vote.

“We have not observed any irregularities in the counting process,” mission chief Esteban Gonzalez Pons said, adding that Colombian electoral law appeared to have been followed.

Petro and his ally, progressive candidate Ivan Cepeda, have challenged the outcome. Petro also alleged fraud after Cepeda failed to win outright in last month’s election.

Cepeda said Sunday his campaign would challenge results from more than 30,000 voting stations and would not recognize the outcome until a recount is completed. Electoral authorities are expected to finish the recount this week.