From the header of murmurcollisions.cc:

 * multicollisions for MurmurHash3
 *
 * MurmurHash3 C++ implementation is available at 
 * http://code.google.com/p/smhasher/wiki/MurmurHash3
 *
 * the function Murmur3Multicollisions finds many different inputs
 * hashing to the same 32-bit value (multicollision)
 * 
 * example output:
 * 32-bit seed 7a0e823a
 * 4-multicollision
 * 16-byte inputs
 * MurmurHash3_x86_32( bdd0c04b5c3995827482773b12acab35 ) = 94d7cf1b
 * MurmurHash3_x86_32( 652fa0565c3946be7482773b12acab35 ) = 94d7cf1b
 * MurmurHash3_x86_32( bdd0c04b5c399582cc23983012ac5c71 ) = 94d7cf1b
 * MurmurHash3_x86_32( 652fa0565c3946becc23983012ac5c71 ) = 94d7cf1b
 *
 * the multicollisions found are "universal": they work for any seed/key
 *
 * authors:
 * Jean-Philippe Aumasson, Daniel J. Bernstein

I consider MurMur3 busted and unsuitable for our purpose.