/usr/lib/x86_64-linux-gnu/libblast.so is in libncbi6-dev 6.1.20120620-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libblast.so.6.1.20120620
/usr/lib/x86_64-linux-gnu/libblast.so.6.1.20120620