At least two Frankfurt Airport employees have died after contracting malaria in an outbreak believed to have been caused by infected mosquitos brought into Germany on an aircraft, according to Frankfurt health officials and Fraport, which operates the airport.

Citing Frankfurt health officials, Germany's DPA news agency reported that the first death occurred in July and that the cause of death was not immediately clear at the time. The second fatality was in August.

The cases are part of a rare outbreak of so-called airport malaria, with six employees infected despite not having traveled to a malaria-risk country.

The other four infected employees are recovering well, health authorities said.

What we know about the Frankfurt Airport malaria death