They were in fuel that was left over after a Titan IVB rocket launched on April 29 from Cape Canaveral, Fla., according to a newly released government report.

The rocket dropped a 10,000-kg booster into the North Atlantic near the Hibernia platform on the Grand Banks, about 350 kilometres east of St. John's.

The report, prepared by Public Safety and Emergency Preparedness Canada, says two chemicals in the fuel – dimethylhydrazine and nitrogen dioxide – are poisonous and corrosive.

Inhaling vapours from the chemicals can kill a person, says the document obtained under the Access to Information Act.

However, Environment Canada told the Canadian Press it doesn't believe the chemicals pose a long-term danger to the Grand Banks.

The rocket mission caused a diplomatic scramble in April, when officials revealed that the booster and other debris would land near oil platforms.

The launch was delayed several times amid fears that the rocket could land on a platform, killing people and possibly causing an ecological disaster.