Twenty-one people died in the explosion of a satellite launch rocket at Brazil’s Alcantara space center near here, aeronautics officials confirmed Saturday.

The prototype launch vehicle was being prepared for Monday’s launch into orbit of two Brazilian observation satellites when it exploded Friday, incinerating the bodies of the victims and destroying the satellites and launch pad.

The space center in Maranhao state was in total lockdown Saturday, with soldiers barring entry to all unauthorized people. Journalists were instructed to talk to official spokespeople, while grieving relatives complained of receiving minimal information.

The explosion was triggered when one of the rocket’s four main thrust engines was unintentionally fired up. The 36-meter(118-foot) platform where the technicians were working disintegrated, officials said.

The remains of only two victims have so far been transfered from the wreckage of the rocket to the Forensic Medical Institute in Sao Luis, due to the extreme degree of incineration of the bodies in the blast.