In a written statement sent to Lusa, ANA - Aeroportos de Portugal states that, "after assessment of the substance by the specialised team of Lisbon firefighters, it was concluded that there is no danger to human health."

ANA did not specify what the substance was that was found on the plane.

According to the company, by 7 p.m. on Friday a security perimeter set up around the plane after the substance was found had been lifted, and the aircraft was “ready to take off soon".

On the ANA website, at 7.15 p.m., it was already stated that passengers flying Swiss International to Zurich, which was to have taken off at 2.35 p.m., were now boarding.

Early on Friday afternoon, an official of Lisbon’s PSP police force told Lusa that a "chemical powder" had been found in the hold of a plane at Humberto Delgado Airport.

The PSP said that it been alerted at 2.59 p.m. and that officers had set up a security perimeter around the plane, with the help of firefighters, which has members trained in using equipment against nuclear, biological and chemical hazards.

A firefighters’ corporation source told Lusa that "ruptured bags" containing a powder had been found, without specifying what the substance was.

Seventeen firefighters and four vehicles were deployed in the operation, according to the website of the National Emergency and Civil Protection Authority.