MEXICO CITY — Mexico requested aid from the U.S. and Canada to investigate a deadly and controversial helicopter crash that occurred Monday. The Canadian help has arrived, but the American support has faced difficulties as a result of the government’s shutdown.

The helicopter crash killed Martha Erika Alonso, governor of the state of Puebla, and her husband and senator, Rafael Moreno Valle.

Alonso and Moreno Valle were strong opponents of president Andrés Manuel López Obrador. That fueled speculation on social media that the federal government may have played a role in the crash.

The president declined to attend the funeral, arguing that it would ignite more attacks. And he said Canada and the U.S. would collaborate on the investigation, to leave no doubts about a conflict of interest.

Mexican officials confirmed that the U.S. National Transportation Safety Board will be able to help despite the U.S. government’s shutdown.