Process gets killed during build

I am building a project on Gitlab CI where I have to run node install --silent during the build.

The whole npm install process takes about 2-3 minutes. A few days ago the build started to fail because the npm process gets killed after a few seconds.

Build output:

npm install --silent
/tmp/executor20160209-536-nvbz2g: line 15:  1886 Killed                  npm install --silent

What is causing this? If i run npm install --silent in the build directory everything works fine.